================================================================= Linux* Open-iSCSI ================================================================= Jun 6, 2022 Contents ======== - 1. In This Release - 2. Introduction - 3. Installation - 4. Open-iSCSI daemon - 5. Open-iSCSI Configuration Utility - 6. Configuration - 7. Getting Started - 8. Advanced Configuration - 9. iSCSI System Info 1. In This Release ================== This file describes the Linux* Open-iSCSI Initiator. The software was tested on AMD Opteron (TM) and Intel Xeon (TM). The latest development release is available at: https://github.com/open-iscsi/open-iscsi For questions, comments, contributions post an issue on github, or send e-mail to: open-iscsi@googlegroups.com You can also raise an issue on the github page. 1.1. Features ============= - highly optimized and very small-footprint data path - persistent configuration database - SendTargets discovery - CHAP - PDU header Digest - multiple sessions 2. Introduction =============== The Open-iSCSI project is a high-performance, transport independent, multi-platform implementation of RFC3720 iSCSI. Open-iSCSI is partitioned into user and kernel parts. The kernel portion of Open-iSCSI was originally part of this project repository, but now is built into the linux kernel itself. It includes loadable modules: scsi_transport_iscsi.ko, libiscsi.ko and scsi_tcp.ko. The kernel code handles the "fast" path, i.e. data flow. User space contains the entire control plane: configuration manager, iSCSI Discovery, Login and Logout processing, connection-level error processing, Nop-In and Nop-Out handling, and (perhaps in the future:) Text processing, iSNS, SLP, Radius, etc. The user space Open-iSCSI consists of a daemon process called iscsid, and a management utility iscsiadm. There are also helper programs, and iscsiuio, which is used for certain iSCSI adapters. 3. Installation =============== NOTE: You will need to be root to install the Open-iSCSI code, and you will also need to be root to run it. As of today, the Open-iSCSI Initiator requires a host running the Linux operating system with kernel. The userspace components iscsid, iscsiadm and iscsistart require the open-isns library. If this package is not available for your distribution, you can download and install it yourself. To install the open-isns headers and library required for Open-iSCSI, download the current release from: https://github.com/open-iscsi/open-isns Then, from the top-level directory, run: ./configure [] make make install For the open-iscsi project and iscsiuio, the original build system used make and autoconf the build the project. These build systems are being depcreated in favor of meson (and ninja). See below for how to build using make and autoconf, but migrating as soon as possible to meson would be a good idea. Building open-iscsi/iscsiuio using meson ---------------------------------------- For Open-iSCSI and iscsiuio, the system is built using meson and ninja (see https://github.com/mesonbuild/meson). If these packages aren't available to you on your Linux distribution, you can download the latest release from: https://github.com/mesonbuild/meson/releases). The README.md file describes in detail how to build it yourself, including how to get ninja. To build the open-iscsi project, including iscsiuio, first run meson to configure the build, from the top-level open-iscsi directory, e.g.: rm -rf builddir mkdir builddir meson [] builddir Then, to build the code: ninja -C builddir If you change any code and want to rebuild, you simply run ninja again. When you are ready to install: [DESTDIR=] ninja -C builddir install This will install the iSCSI tools, configuration files, interfaces, and documentation. If you do not set DESTDIR, it defaults to "/". MESON-OPTIONS: -------------- One can override several default values when building with meson: - Library files are installed in /lib64 by default, but this can be overridden by passing '--libdir=' to meson. - Extra flags can be passed to the C compiler using '-Dc_flags=""'. - In newer version of meson (>=0.63) you can override location where binaries are installed, which by default is "/usr/sbin", using the '--sbindir=' option to meson. - The default "home" directory is "/etc/iscsi", but this can be overridden using '-Dhomedir='. This is where the configuration files are kept - The default "database" directory is also "/etc/iscsi", but can be overridden using '-Ddbroot=' Building open-iscsi/iscsiuio using make/autoconf ------------------------------------------------ If you wish to build using the older deprecated system, you can simply run: make [] make [DESTDIR=] install Where MAKE-OPTIONS are from: * SBINDIR= [/usr/bin] for executables * DBROOT= [/etc/iscsi] for iscsi database files * HOMEDIR= [/etc/iscsi] for iscsi config files 4. Open-iSCSI daemon ==================== The iscsid daemon implements control path of iSCSI protocol, plus some anagement facilities. For example, the daemon could be configured to utomatically re-start discovery at startup, based on the contents of ersistent iSCSI database (see next section). For help, run: iscsid --help The output will be similar to the following (assuming a default install): Usage: iscsid [OPTION] -c, --config=[path] Execute in the config file (/etc/iscsi/iscsid.conf). -i, --initiatorname=[path] read initiatorname from file (/etc/iscsi/initiatorname.iscsi). -f, --foreground run iscsid in the foreground -d, --debug debuglevel print debugging information -u, --uid=uid run as uid, default is current user -g, --gid=gid run as gid, default is current user group -n, --no-pid-file do not use a pid file -p, --pid=pidfile use pid file (default /run/iscsid.pid). -h, --help display this help and exit -v, --version display version and exit 5. Open-iSCSI Configuration and Administration Utility ====================================================== Open-iSCSI persistent configuration is stored in a number of directories under a configuration root directory, using a flat-file format. This configuration root directory is /etc/iscsi by default, but may also commonly be in /var/lib/iscsi (see "dbroot" in the meson options discussed earlier). Configuration is contained in directories for: - nodes - slp - isns - static - fw - send_targets - ifaces The iscsiadm utility is a command-line tool to manage (update, delete, insert, query) the persistent database, as well manage discovery, session establishment (login), and ending sessions (logout). This utility presents set of operations that a user can perform on iSCSI node, session, connection, and discovery records. Open-iSCSI does not use the term node as defined by the iSCSI RFC, where a node is a single iSCSI initiator or target. Open-iSCSI uses the term node to refer to a portal on a target, so tools like iscsiadm require that the '--targetname' and '--portal' arguments be used when in node mode. For session mode, a session id (sid) is used. The sid of a session can be found by running: iscsiadm -m session -P 1 The session id is not currently persistent and is partially determined by when the session is setup. Note that some of the iSCSI Node and iSCSI Discovery operations do not require iSCSI daemon (iscsid) loaded. For help on the command, run: iscsiadm --help The output will be similar to the following. iscsiadm -m discoverydb [-hV] [-d debug_level] [-P printlevel] [-t type -p ip:port -I ifaceN ... [-Dl]] | [[-p ip:port -t type] [-o operation] [-n name] [-v value] [-lD]] iscsiadm -m discovery [-hV] [-d debug_level] [-P printlevel] [-t type -p ip:port -I ifaceN ... [-l]] | [[-p ip:port] [-l | -D]] [-W] iscsiadm -m node [-hV] [-d debug_level] [-P printlevel] [-L all,manual,automatic,onboot] [-W] [-U all,manual,automatic,onboot] [-S] [[-T targetname -p ip:port -I ifaceN] [-l | -u | -R | -s]] [[-o operation ] [-n name] [-v value]] iscsiadm -m session [-hV] [-d debug_level] [-P printlevel] [-r sessionid | sysfsdir [-R | -u | -s] [-o operation] [-n name] [-v value]] iscsiadm -m iface [-hV] [-d debug_level] [-P printlevel] [-I ifacename | -H hostno|MAC] [[-o operation ] [-n name] [-v value]] [-C ping [-a ip] [-b packetsize] [-c count] [-i interval]] iscsiadm -m fw [-d debug_level] [-l] [-W] [[-n name] [-v value]] iscsiadm -m host [-P printlevel] [-H hostno|MAC] [[-C chap [-x chap_tbl_idx]] | [-C flashnode [-A portal_type] [-x flashnode_idx]] | [-C stats]] [[-o operation] [-n name] [-v value]] iscsiadm -k priority The first parameter specifies the mode to operate in: -m, --mode specify operational mode op = Mode "discoverydb" ------------------ -m discoverydb --type=[type] --interface=[iface…] --portal=[ip:port] \ --print=[N] \ --op=[op]=[NEW | UPDATE | DELETE | NONPERSISTENT] \ --discover This command will use the discovery record settings matching the record with type=type and portal=ip:port]. If a record does not exist, it will create a record using the iscsid.conf discovery settings. By default, it will then remove records for portals no longer returned. And, if a portal is returned by the target, then the discovery command will create a new record or modify an existing one with values from iscsi.conf and the command line. [op] can be passed in multiple times to this command, and it will alter the node DB manipulation. If [op] is passed in and the value is "new", iscsiadm will add records for portals that do not yet have records in the db. If [op] is passed in and the value is "update", iscsiadm will update node records using info from iscsi.conf and the command line for portals that are returned during discovery and have a record in the db. If [op] is passed in and the value is "delete", iscsiadm will delete records for portals that were not returned during discovery. If [op] is passed in and the value is "nonpersistent", iscsiadm will not store the portals found in the node DB. This is only useful with the --login command. See the example section for more info. See below for how to setup iSCSI ifaces for software iSCSI or override the system defaults. Multiple ifaces can be passed in during discovery. For the above commands, "print" is optional. If used, N can be 0 or 1. 0 = The old flat style of output is used. 1 = The tree style with the inteface info is used. If print is not used, the old flat style is used. -m discoverydb --interface=[iface...] --type=[type] --portal=[ip:port] \ --print=[N] \ --op=[op]=[NEW | UPDATE | DELETE | NONPERSISTENT] \ --discover --login This works like the previous discoverydb command with the --login argument passed in will also log into the portals that are found. -m discoverydb --portal=[ip:port] --type=[type] \ --op=[op] [--name=[name] --value=[value]] Perform specific DB operation [op] for discovery portal. It could be one of: [new], [delete], [update] or [show]. In case of [update], you have to provide [name] and [value] you wish to update Setting op=NEW will create a new discovery record using the iscsid.conf discovery settings. If it already exists, it will be overwritten using iscsid.conf discovery settings. Setting op=DELETE will delete the discovery record and records for the targets found through Phat discovery source. Setting op=SHOW will display the discovery record values. The --show argument can be used to force the CHAP passwords to be displayed. Mode "discovery" ---------------- -m discovery --type=[type] --interface=iscsi_ifacename \ --portal=[ip:port] --login --print=[N] \ --op=[op]=[NEW | UPDATE | DELETE | NONPERSISTENT] Perform [type] discovery for target portal with ip-address [ip] and port [port]. This command will not use the discovery record settings. It will use the iscsid.conf discovery settings and it will overwrite the discovery record with iscsid.conf discovery settings if it exists. By default, it will then remove records for portals no longer returned. And, if a portal is returned by the target, then the discovery command will create a new record or modify an existing one with values from iscsi.conf and the command line. [op] can be passed in multiple times to this command, and it will alter the DB manipulation. If [op] is passed in and the value is "new", iscsiadm will add records for portals that do not yet have records in the db. If [op] is passed in and the value is "update", iscsiadm will update node records using info from iscsi.conf and the command line for portals that are returned during discovery and have a record in the db. If [op] is passed in and the value is "delete", iscsiadm will delete records for portals that were not returned during discovery. If [op] is passed in and the value is "nonpersistent", iscsiadm will not store the portals found in the node DB. See the example section for more info. See below for how to setup iSCSI ifaces for software iSCSI or override the system defaults. Multiple ifaces can be passed in during discovery. -m discovery --print=[N] Display all discovery records from internal persistent discovery database. Mode "node" ----------- -m node display all discovered nodes from internal persistent discovery database -m node --targetname=[name] --portal=[ip:port] \ --interface=iscsi_ifacename] \ [--login|--logout|--rescan|--stats] [-W] -m node --targetname=[name] --portal=[ip:port] --interface=[driver,HWaddress] \ --op=[op] [--name=[name] --value=[value]] -m node --targetname=[name] --portal=[ip:port] --interface=iscsi_ifacename] \ --print=[level] Perform specific DB operation [op] for specific interface on host that will connect to portal on target. targetname, portal and interface are optional. See below for how to setup iSCSI ifaces for software iSCSI or override the system defaults. The op could be one of [new], [delete], [update] or [show]. In case of [update], you have to provide [name] and [value] you wish to update. For [delete], note that if a session is using the node record, the session will be logged out then the record will be deleted. Using --rescan will perform a SCSI layer scan of the session to find new LUNs. Using --stats prints the iSCSI stats for the session. Using --login normally sends a login request to the specified target and normally waits for the results. If -W/--no_wait is supplied return success if we are able to send the login request, and do not wait for the response. The user will have to poll for success Print level can be 0 to 1. -m node --logoutall=[all|manual|automatic] Logout "all" the running sessions or just the ones with a node startup value manual or automatic. Nodes marked as ONBOOT are skipped. -m node --loginall=[all|manual|automatic] [-W] Login "all" the running sessions or just the ones with a node startup value manual or automatic. Nodes marked as ONBOOT are skipped. If -W is supplied then do not wait for the login response for the target, returning success if we are able to just send the request. The client will have to poll for success. Mode "session" -------------- -m session display all active sessions and connections -m session --sid=[sid] [ --print=level | --rescan | --logout ] --op=[op] [--name=[name] --value=[value]] Perform operation for specific session with session id sid. If no sid is given, the operation will be performed on all running sessions if possible. --logout and --op work like they do in node mode, but in session mode targetname and portal info is not passed in. Print level can be 0 to 2. 1 = Print basic session info like node we are connected to and whether we are connected. 2 = Print iSCSI params used. 3 = Print SCSI info like LUNs, device state. If no sid and no operation is given print out the running sessions. Mode "iface" ------------ -m iface --interface=iscsi_ifacename --op=[op] [--name=[name] --value=[value]] --print=level Perform operation on given interface with name iscsi_ifacename. See below for examples. -m iface --interface=iscsi_ifacename -C ping --ip=[ipaddr] --packetsize=[size] --count=[count] --interval=[interval] Mode "host" ----------- -m host [--host=hostno|MAC] --print=level -C chap --op=[SHOW] Display information for a specific host. The host can be passed in by host number or by MAC address. If a host is not passed in, then info for all hosts is printed. Print level can be 0 to 4. 1 = Print info for how like its state, MAC, and netinfo if possible. 2 = Print basic session info for nodes the host is connected to. 3 = Print iSCSI params used. 4 = Print SCSI info like LUNs, device state. -m host --host=hostno|MAC -C chap --op=[DELETE] --index=[chap_tbl_idx] Delete chap entry at the given index from chap table. -m host --host=hostno|MAC -C chap --op=[NEW | UPDATE] --index=[chap_tbl_idx] \ --name=[name] --value=[value] Add new or update existing chap entry at the given index with given username and password pair. If index is not passed then entry is added at the first free index in chap table. -m host --host=hostno|MAC -C flashnode Display list of all the targets in adapter's flash (flash node), for the specified host, with ip, port, tpgt and iqn. -m host --host=hostno|MAC -C flashnode --op=[NEW] --portal_type=[ipv4|ipv6] Create new flash node entry for the given host of the specified portal_type. This returns the index of the newly created entry on success. -m host --host=hostno|MAC -C flashnode --index=[flashnode_index] \ --op=[UPDATE] --name=[name] --value=[value] Update the params of the speficied flash node. The [name] and [value] pairs must be provided for the params that need to be updated. Multiple params can be updated using a single command. -m host --host=hostno|MAC -C flashnode --index=[flashnode_index] \ --op=[SHOW | DELETE | LOGIN | LOGOUT] Setting op=DELETE|LOGIN|LOGOUT will perform deletion/login/ logout operation on the specified flash node. Setting op=SHOW will list all params with the values for the specified flash node. This is the default operation. See the iscsiadm example section below for more info. Other arguments --------------- -d, --debug debuglevel print debugging information -V, --version display version and exit -h, --help display this help and exit 5.1 iSCSI iface setup ===================== The next sections describe how to setup iSCSI ifaces so you can bind a session to a NIC port when using software iSCSI (section 5.1.1), and it describes how to setup ifaces for use with offload cards from Chelsio and Broadcom (section 5.1.2). 5.1.1 How to setup iSCSI interfaces (iface) for binding ======================================================= If you wish to allow the network susbsystem to figure out the best path/NIC to use, then you can skip this section. For example if you have setup your portals and NICs on different subnets, then the following is not needed for software iSCSI. Warning!!!!!! This feature is experimental. The interface may change. When reporting bugs, if you cannot do a "ping -I ethX target_portal", then check your network settings first. Make sure the rp_filter setting is set to 0 or 2 (see Prep section below for more info). If you cannot ping the portal, then you will not be able to bind a session to a NIC. What is a scsi_host and iface for software, hardware and partial offload iSCSI? Software iSCSI, like iscsi_tcp and iser, allocates a scsi_host per session and does a single connection per session. As a result /sys/class_scsi_host and /proc/scsi will report a scsi_host for each connection/session you have logged into. Offload iSCSI, like Chelsio cxgb3i, allocates a scsi_host for each PCI device (each port on a HBA will show up as a different PCI device so you get a scsi_host per HBA port). To manage both types of initiator stacks, iscsiadm uses the interface (iface) structure. For each HBA port or for software iSCSI for each network device (ethX) or NIC, that you wish to bind sessions to you must create a iface config /etc/iscsi/ifaces. Prep ---- The iface binding feature requires the sysctl setting net.ipv4.conf.default.rp_filter to be set to 0 or 2. This can be set in /etc/sysctl.conf by having the line: net.ipv4.conf.default.rp_filter = N where N is 0 or 2. Note that when setting this you may have to reboot for the value to take effect. rp_filter information from Documentation/networking/ip-sysctl.txt: rp_filter - INTEGER 0 - No source validation. 1 - Strict mode as defined in RFC3704 Strict Reverse Path Each incoming packet is tested against the FIB and if the interface is not the best reverse path the packet check will fail. By default failed packets are discarded. 2 - Loose mode as defined in RFC3704 Loose Reverse Path Each incoming packet's source address is also tested against the FIB and if the source address is not reachable via any interface the packet check will fail. Running ------- The command: iscsiadm -m iface will report iface configurations that are setup in /etc/iscsi/ifaces: iface0 qla4xxx,00:c0:dd:08:63:e8,20.15.0.7,default,iqn.2005-06.com.redhat:madmax iface1 qla4xxx,00:c0:dd:08:63:ea,20.15.0.9,default,iqn.2005-06.com.redhat:madmax The format is: iface_name transport_name,hwaddress,ipaddress,net_ifacename,initiatorname For software iSCSI, you can create the iface configs by hand, but it is recommended that you use iscsiadm's iface mode. There is an iface.example in /etc/iscsi/ifaces which can be used as a template for the daring. For each network object you wish to bind a session to, you must create a separate iface config in /etc/iscsi/ifaces and each iface config file must have a unique name which is less than or equal to 64 characters. Example ------- If you have NIC1 with MAC address 00:0F:1F:92:6B:BF and NIC2 with MAC address 00:C0:DD:08:63:E7, and you wanted to do software iSCSI over TCP/IP, then in /etc/iscsi/ifaces/iface0 you would enter: iface.transport_name = tcp iface.hwaddress = 00:0F:1F:92:6B:BF and in /etc/iscsi/ifaces/iface1 you would enter: iface.transport_name = tcp iface.hwaddress = 00:C0:DD:08:63:E7 Warning: Do not name an iface config file "default" or "iser". They are special values/files that are used by the iSCSI tools for backward compatibility. If you name an iface default or iser, then the behavior is not defined. To use iscsiadm to create an iface0 similar to the above example, run: iscsiadm -m iface -I iface0 --op=new (This will create a new empty iface config. If there was already an iface with the name "iface0", this command will overwrite it.) Next, set the hwaddress: iscsiadm -m iface -I iface0 --op=update \ -n iface.hwaddress -v 00:0F:1F:92:6B:BF If you had sessions logged in, iscsiadm will not update or overwrite an iface. You must log out first. If you have an iface bound to a node/portal but you have not logged in, then iscsiadm will update the config and all existing bindings. You should now skip to 5.1.3 to see how to log in using the iface, and for some helpful management commands. 5.1.2 Setting up an iface for an iSCSI offload card =================================================== This section describes how to setup ifaces for use with Chelsio, Broadcom and QLogic cards. By default, iscsiadm will create an iface for each Broadcom, QLogic and Chelsio port. The iface name will be of the form: $transport/driver_name.$MAC_ADDRESS Running the following command: iscsiadm -m iface will report iface configurations that are setup in /etc/iscsi/ifaces: default tcp,,,, iser iser,,,, cxgb3i.00:07:43:05:97:07 cxgb3i,00:07:43:05:97:07,,, qla4xxx.00:0e:1e:04:8b:2e qla4xxx,00:0e:1e:04:8b:2e,,, The format is: iface_name transport_name,hwaddress,ipaddress,net_ifacename,initiatorname where: iface_name: name of iface transport_name: name of driver hwaddress: MAC address ipaddress: IP address to use for this port net_iface_name: will be because change between reboots. It is used for software iSCSI's vlan or alias binding. initiatorname: Initiatorname to be used if you want to override the default one in /etc/iscsi/initiatorname.iscsi. To display these values in a more friendly way, run: iscsiadm -m iface -I cxgb3i.00:07:43:05:97:07 Example output: # BEGIN RECORD 2.0-871 iface.iscsi_ifacename = cxgb3i.00:07:43:05:97:07 iface.net_ifacename = iface.ipaddress = iface.hwaddress = 00:07:43:05:97:07 iface.transport_name = cxgb3i iface.initiatorname = # END RECORD Before you can use the iface, you must set the IP address for the port. We determine the corresponding variable name that we want to update from the output above, which is "iface.ipaddress". Then we fill this empty variable with the value we desire, with this command: iscsiadm -m iface -I cxgb3i.00:07:43:05:97:07 -o update \ -n iface.ipaddress -v 20.15.0.66 Note for QLogic ports: After updating the iface record, you must apply or applyall the settings for the changes to take effect: iscsiadm -m iface -I qla4xxx.00:0e:1e:04:8b:2e -o apply iscsiadm -m iface -H 00:0e:1e:04:8b:2e -o applyall With "apply", the network settings for the specified iface will take effect. With "applyall", the network settings for all ifaces on a specific host will take effect. The host can be specified using the -H/--host argument by either the MAC address of the host or the host number. Here is an example of setting multiple IPv6 addresses on a single iSCSI interface port. First interface (no need to set iface_num, it is 0 by default): iscsiadm -m iface -I qla4xxx.00:0e:1e:04:8b:2a -o update \ -n iface.ipaddress -v fec0:ce00:7014:0041:1111:2222:1e04:9392 Create the second interface if it does not exist (iface_num is mandatory here): iscsiadm -m iface -I qla4xxx.00:0e:1e:04:8b:2a.1 -op=new iscsiadm -m iface -I qla4xxx.00:0e:1e:04:8b:2a -o update \ -n iface.iface_num -v 1 iscsiadm -m iface -I qla4xxx.00:0e:1e:04:8b:2a -o update \ -n iface.ipaddress -v fec0:ce00:7014:0041:1111:2222:1e04:9393 iscsiadm -m iface -H 00:0e:1e:04:8b:2a --op=applyall Note: If there are common settings for multiple interfaces then the settings from 0th iface would be considered valid. Now, we can use this iface to login into targets, which is described in the next section. 5.1.3 Discovering iSCSI targets/portals ======================================== Be aware that iscsiadm will use the default route to do discovery. It will not use the iface specified. So if you are using an offload card, you will need a separate network connection to the target for discovery purposes. *This should be fixed in the some future version of Open-iSCSI* For compatibility reasons, when you run iscsiadm to do discovery, it will check for interfaces in /etc/iscsi/iscsi/ifaces that are using tcp for the iface.transport, and it will bind the portals that are discovered so that they will be logged in through those ifaces. This behavior can also be overridden by passing in the interfaces you want to use. For the case of offload, like with cxgb3i and bnx2i, this is required because the transport will not be tcp. For example if you had defined two interfaces but only wanted to use one, you can use the --interface/-I argument: iscsiadm -m discoverydb -t st -p ip:port -I iface1 --discover -P 1 If you had defined interfaces but wanted the old behavior, where we do not bind a session to an iface, then you can use the special iface "default": iscsiadm -m discoverydb -t st -p ip:port -I default --discover -P 1 And if you did not define any interfaces in /etc/iscsi/ifaces and do not pass anything into iscsiadm, running iscsiadm will do the default behavior, allowing the network subsystem to decide which device to use. If you later want to remove the bindings for a specific target and iface, then you can run: iscsiadm -m node -T my_target -I iface0 --op=delete To do this for a specific portal on a target, run: iscsiadm -m node -T my_target -p ip:port -I iface0 --op=delete If you wanted to delete all bindinds for iface0, then you can run: iscsiadm -m node -I iface0 --op=delete And for equalogic targets it is sometimes useful to remove just by portal: iscsiadm -m node -p ip:port -I iface0 --op=delete Now logging into targets is the same as with software iSCSI. See section 7 for how to get started. 5.2 iscsiadm examples ===================== Usage examples using the one-letter options (see iscsiadm man page for long options): Discovery mode -------------- - SendTargets iSCSI Discovery using the default driver and interface and using the discovery settings for the discovery record with the ID [192.168.1.1:3260]: iscsiadm -m discoverydb -t st -p 192.168.1.1:3260 --discover This will search /etc/iscsi/send_targets for a record with the ID [portal = 192.168.1.1:3260 and type = sendtargets. If found it will perform discovery using the settings stored in the record. If a record does not exist, it will be created using the iscsid.conf discovery settings. The argument to -p may also be a hostname instead of an address: iscsiadm -m discoverydb -t st -p somehost --discover For the ifaces, iscsiadm will first search /etc/iscsi/ifaces for interfaces using software iSCSI. If any are found then nodes found during discovery will be setup so that they can logged in through those interfaces. To specify a specific iface, pass the -I argument for each iface. - SendTargets iSCSI Discovery updating existing target records: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o update --discover If there is a record for targetX, and portalY exists in the DB, and is returned during discovery, it will be updated with the info from the iscsi.conf. No new portals will be added and stale portals will not be removed. - SendTargets iSCSI Discovery deleting existing target records: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o delete --discover If there is a record for targetX, and portalY exists in the DB, but is not returned during discovery, it will be removed from the DB. No new portals will be added and existing portal records will not be changed. Note: If a session is logged into portal we are going to delete a record for, it will be logged out then the record will be deleted. - SendTargets iSCSI Discovery adding new records: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o new --discover If there is targetX, and portalY is returned during discovery, and does not have a record, it will be added. Existing records are not modified. - SendTargets iSCSI Discovery using multiple ops: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o new -o delete --discover This command will add new portals and delete records for portals no longer returned. It will not change the record information for existing portals. - SendTargets iSCSI Discovery in nonpersistent mode: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o nonpersistent --discover This command will perform discovery, but not manipulate the node DB. - SendTargets iSCSI Discovery with a specific interface. If you wish to only use a subset of the interfaces in /etc/iscsi/ifaces, then you can pass them in during discovery: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ --interface=iface0 --interface=iface1 --discover Note that for software iSCSI, we let the network layer select which NIC to use for discovery, but for later logins iscsiadm will use the NIC defined in the iface configuration. qla4xxx support is very basic and experimental. It does not store the record info in the card's FLASH or the node DB, so you must rerun discovery every time the driver is reloaded. - Manipulate SendTargets DB: Create new SendTargets discovery record or overwrite an existing discovery record with iscsid.conf discovery settings: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 -o new - Manipulate SendTargets DB: Display discovery settings: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 -o show - Manipulate SendTargets DB: Display hidden discovery settings like CHAP passwords: iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o show --show - Manipulate SendTargets DB: Set discovery setting. iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 \ -o update -n name -v value - Manipulate SendTargets DB: Delete discovery record. This will also delete the records for the targets found through the discovery source. iscsiadm -m discoverydb -t sendtargets -p 192.168.1.1:3260 -o delete - Show all records in discovery database: iscsiadm -m discovery - Show all records in discovery database and show the targets that were discovered from each record: iscsiadm -m discovery -P 1 Node mode --------- In node mode you can specify which records you want to log into by specifying the targetname, ip address, port or interface (if specifying the interface it must already be setup in the node db). iscsiadm will search the node db for records which match the values you pass in, so if you pass in the targetname and interface, iscsiadm will search for records with those values and operate on only them. Passing in none of them will result in all node records being operated on. - iSCSI Login to all portals on every node/starget through each interface set in the db: iscsiadm -m node -l - iSCSI login to all portals on a node/target through each interface set in the db, but do not wait for the login response: iscsiadm -m node -T iqn.2005-03.com.max -l -W - iSCSI login to a specific portal through each interface set in the db: iscsiadm -m node -T iqn.2005-03.com.max -p 192.168.0.4:3260 -l To specify an iPv6 address, the following can be used: iscsiadm -m node -T iqn.2005-03.com.max \ -p 2001:c90::211:9ff:feb8:a9e9 -l The above command would use the default port, 3260. To specify a port, use the following: iscsiadm -m node -T iqn.2005-03.com.max \ -p [2001:c90::211:9ff:feb8:a9e9]:3260 -l To specify a hostname, the following can be used: iscsiadm -m node -T iqn.2005-03.com.max -p somehost -l - iSCSI Login to a specific portal through the NIC setup as iface0: iscsiadm -m node -T iqn.2005-03.com.max -p 192.168.0.4:3260 \ -I iface0 -l - iSCSI Logout of all portals on every node/starget through each interface set in the db: iscsiadm -m node -u Warning: this does not check startup values like the logout/login all option. Do not use this if you are running iSCSI on your root disk. - iSCSI logout of all portals on a node/target through each interface set in the db: iscsiadm -m node -T iqn.2005-03.com.max -u - iSCSI logout of a specific portal through each interface set in the db: iscsiadm -m node -T iqn.2005-03.com.max -p 192.168.0.4:3260 -u - iSCSI Logout of a specific portal through the NIC setup as iface0: iscsiadm -m node -T iqn.2005-03.com.max -p 192.168.0.4:3260 \ -I iface0 - Changing iSCSI parameter: iscsiadm -m node -T iqn.2005-03.com.max -p 192.168.0.4:3260 \ -o update -n node.cnx[0].iscsi.MaxRecvDataSegmentLength -v 65536 You can also change parameters for multiple records at once, by specifying different combinations of target, portal and interface like above. - Adding custom iSCSI portal: iscsiadm -m node -o new -T iqn.2005-03.com.max \ -p 192.168.0.1:3260,2 -I iface4 The -I/--interface is optional. If not passed in, "default" is used. For tcp or iser, this would allow the network layer to decide what is best. Note that for this command, the Target Portal Group Tag (TPGT) should be passed in. If it is not passed in on the initial creation command, then the user must run iscsiadm again to set the value. Also, if the TPGT is not initially passed in, the old behavior of not tracking whether the record was statically or dynamically created is used. - Adding custom NIC config to multiple targets: iscsiadm -m node -o new -I iface4 This command will add an interface config using the iSCSI and SCSI settings from iscsid.conf to every target that is in the node db. - Removing iSCSI portal: iscsiadm -m node -o delete -T iqn.2005-03.com.max -p 192.168.0.4:3260 You can also delete multiple records at once, by specifying different combinations of target, portal and interface like above. - Display iSCSI portal onfiguration: iscsiadm -m node [-o show] -T iqn.2005-03.com.max -p 192.168.0.4:3260 You can also display multiple records at once, by specifying different combinations of target, portal and interface like above. Note: running "iscsiadm -m node" will only display the records. It will not display the configuration info. For the latter, run: iscsiadm -m node -o show - Show all node records: iscsiadm -m node This will print the nodes using the old flat format where the interface and driver are not displayed. To display that info use the -P option with the argument "1": iscsiadm -m node -P 1 Session mode ------------ - Display session statistics: iscsiadm -m session -r 1 --stats This function also works in node mode. Instead of the "-r $sid" argument, you would pass in the node info like targetname and/or portal, and/or interface. - Perform a SCSI scan on a session iscsiadm -m session -r 1 --rescan This function also works in node mode. Instead of the "-r $sid" argument, you would pass in the node info like targetname and/or portal, and/or interface. Note: Rescanning does not delete old LUNs. It will only pick up new ones. - Display running sessions: iscsiadm -m session -P 1 Host mode with flashnode submode -------------------------------- - Display list of flash nodes for a host iscsiadm -m host -H 6 -C flashnode This will print list of all the flash node entries for the given host along with their ip, port, tpgt and iqn values. - Display all parameters of a flash node entry for a host iscsiadm -m host -H 6 -C flashnode -x 0 This will list all the parameter name,value pairs for the flash node entry at index 0 of host 6. - Add a new flash node entry for a host iscsiadm -m host -H 6 -C flashnode -o new -A [ipv4|ipv6] This will add new flash node entry for the given host 6 with portal type of either ipv4 or ipv6. The new operation returns the index of the newly created flash node entry. - Update a flashnode entry iscsiadm -m host -H 6 -C flashnode -x 1 -o update \ -n flashnode.conn[0].ipaddress -v 192.168.1.12 \ -n flashnode.session.targetname \ -v iqn.2002-03.com.compellent:5000d310004b0716 This will update the values of ipaddress and targetname params of the flash node entry at index 1 of host 6. - Login to a flash node entry iscsiadm -m host -H 6 -C flashnode -x 1 -o login - Logout from a flash node entry Logout can be performed either using the flash node index: iscsiadm -m host -H 6 -C flashnode -x 1 -o logout or by using the corresponding session index: iscsiadm -m session -r $sid -u - Delete a flash node entry iscsiadm -m host -H 6 -C flashnode -x 1 -o delete Host mode with chap submode --------------------------- - Display list of chap entries for a host iscsiadm -m host -H 6 -C chap -o show - Delete a chap entry for a host iscsiadm -m host -H 6 -C chap -o delete -x 5 This will delete any chap entry present at index 5. - Add/Update a local chap entry for a host iscsiadm -m host -H 6 -C chap -o update -x 4 -n username \ -v value -n password -v value This will update the local chap entry present at index 4. If index 4 is free, then a new entry of type local chap will be created at that index with given username and password values. - Add/Update a bidi chap entry for a host iscsiadm -m host -H 6 -C chap -o update -x 5 -n username_in \ -v value -n password_in -v value This will update the bidi chap entry present at index 5. If index 5 is free then entry of type bidi chap will be created at that index with given username_in and password_in values. Host mode with stats submode ---------------------------- - Display host statistics: iscsiadm -m host -H 6 -C stats This will print the aggregate statistics on the host adapter port. This includes MAC, TCP/IP, ECC & iSCSI statistics. 6. Configuration ================ The default configuration file is /etc/iscsi/iscsid.conf, but the directory is configurable with the top-level make option "homedir". The remainder of this document will assume the /etc/iscsi directory. This file contains only configuration that could be overwritten by iSCSI discovery, or manually updated via iscsiadm utility. Its OK if this file does not exist, in which case compiled-in default configuration will take place for newer discovered Target nodes. See the man page and the example file for the current syntax. The manual pages for iscsid, iscsiadm are in the doc subdirectory and can be installed in the appropriate man page directories and need to be manually copied into e.g. /usr/local/share/man8. 7. Getting Started ================== There are three steps needed to set up a system to use iSCSI storage: 7.1. iSCSI startup using the systemd units or manual startup. 7.2. Discover targets. 7.3. Automate target logins for future system reboots. The systemd startup units will start the iSCSI daemon and log into any portals that are set up for automatic login (discussed in 7.2) or discovered through the discover daemon iscsid.conf params (discussed in 7.1.2). If your distro does not have systemd units for iSCSI, then you will have to start the daemon and log into the targets manually. 7.1.1 iSCSI startup using the init script ========================================= Red Hat or Fedora: ----------------- To start Open-iSCSI in Red Hat/Fedora you can do: systemctl start open-iscsi To get Open-iSCSI to automatically start at run time you may have to run: systemctl enable open-iscsi And, to automatically mount a file system during startup you must have the partition entry in /etc/fstab marked with the "_netdev" option. For example this would mount an iSCSI disk sdb: /dev/sdb /mnt/iscsi ext3 _netdev 0 0 SUSE or Debian: --------------- The Open-iSCSI service is socket activated, so there is no need to enable the Open-iSCSI service. Likewise, the iscsi.service login service is enabled automatically, so setting 'startup' to "automatic' will enable automatic login to Open-iSCSI targets. 7.1.2 Manual Startup ==================== 7.1.2.1 Starting up the iSCSI daemon (iscsid) and loading modules ================================================================= If there is no initd script, you must start the tools by hand. First load the iSCSI modules: modprobe -q iscsi_tcp After that, start iSCSI as a daemon process: iscsid or alternatively, start it with debug enabled, in a separate window, which will force it into "foreground" mode: iscsid -d 8 7.1.2.2 Logging into Targets ============================ Use the configuration utility, iscsiadm, to add/remove/update Discovery records, iSCSI Node records or monitor active iSCSI sessions (see above or the iscsiadm man files and see section 7.2 below for how to discover targets): iscsiadm -m node This will print out the nodes that have been discovered as: 10.15.85.19:3260,3 iqn.1992-08.com.netapp:sn.33615311 10.15.84.19:3260,2 iqn.1992-08.com.netapp:sn.33615311 The format is: ip:port,target_portal_group_tag targetname If you are using the iface argument or want to see the driver info, use the following: iscsiadm -m node -P 1 Example output: Target: iqn.1992-08.com.netapp:sn.33615311 Portal: 10.15.84.19:3260,2 Iface Name: iface2 Portal: 10.15.85.19:3260,3 Iface Name: iface2 The format is: Target: targetname Portal ip_address:port,tpgt Iface: ifacename Here, where targetname is the name of the target and ip_address:port is the address and port of the portal. tpgt is the Target Portal Group Tag of the portal, and is not used in iscsiadm commands except for static record creation. ifacename is the name of the iSCSI interface defined in /etc/iscsi/ifaces. If no interface was defined in /etc/iscsi/ifaces or passed in, the default behavior is used. Default here is iscsi_tcp/tcp to be used over whichever NIC the network layer decides is best. To login, take the ip, port and targetname from above and run: iscsiadm -m node -T targetname -p ip:port -l In this example we would run: iscsiadm -m node -T iqn.1992-08.com.netapp:sn.33615311 \ -p 10.15.84.19:3260 -l Note: drop the portal group tag from the "iscsiadm -m node" output. If you wish, for example to login to all targets represented in the node database, but not wait for the login responses: iscsiadm -m node -l -W After this, you can use "session" mode to detect when the logins complete: iscsiadm -m session 7.2. Discover Targets ===================== Once the iSCSI service is running, you can perform discovery using SendTarget with: iscsiadm -m discoverydb -t sendtargets -p ip:port --discover Here, "ip" is the address of the portal and "port" is the port. To use iSNS you can run the discovery command with the type as "isns" and pass in the ip:port: iscsiadm -m discoverydb -t isns -p ip:port --discover Both commands will print out the list of all discovered targets and their portals, e.g.: iscsiadm -m discoverydb -t st -p 10.15.85.19:3260 --discover This might produce: 10.15.84.19:3260,2 iqn.1992-08.com.netapp:sn.33615311 10.15.85.19:3260,3 iqn.1992-08.com.netapp:sn.33615311 The format for the output is: ip:port,tpgt targetname In this example, for the first target the ip address is 10.15.85.19, and the port is 3260. The target portal group is 3. The target name is iqn.1992-08.com.netapp:sn.33615311. If you would also like to see the iSCSI inteface which will be used for each session then use the --print=[N]/-P [N] option: iscsiadm -m discoverydb -t sendtargets -p ip:port -P 1 --discover This might print: Target: iqn.1992-08.com.netapp:sn.33615311 Portal: 10.15.84.19:3260,2 Iface Name: iface2 Portal: 10.15.85.19:3260,3 Iface Name: iface2 In this example, the IP address of the first portal is 10.15.84.19, and the port is 3260. The target portal group is 3. The target name is iqn.1992-08.com.netapp:sn.33615311. The iface being used is iface2. While discovery targets are kept in the discovery db, they are useful only for re-discovery. The discovered targets (a.k.a. nodes) are stored as records in the node db. The discovered targets are not logged into yet. Rather than logging into the discovered nodes (making LUs from those nodes available as storage), it is better to automate the login to the nodes we need. If you wish to log into a target manually now, see section "7.1.2.2 Logging in targets" above. 7.3. Automate Target Logins for Future System Startups ====================================================== Note: this may only work for distros with systemd iSCSI login scripts. To automate login to a node, use the following with the record ID (record ID is the targetname and portal) of the node discovered in the discovery above: iscsiadm -m node -T targetname -p ip:port --op update -n node.startup -v automatic To set the automatic setting to all portals on a target through every interface setup for each protal, the following can be run: iscsiadm -m node -T targetname --op update -n node.startup -v automatic Or to set the "node.startup" attribute to "automatic" as default for all sessions add the following to the /etc/iscsi/iscsid.conf: node.startup = automatic Setting this in iscsid.conf will not affect existing nodes. It will only affect nodes that are discovered after setting the value. To login to all automated nodes, simply restart the iSCSI login service, e.g. with: systemctl restart iscsi.service On your next startup the nodes will be logged into automatically. 7.4 Automatic Discovery and Login ================================= Instead of running the iscsiadm discovery command and editing the startup setting, iscsid can be configured so that every X seconds it performs discovery and logs in and out of the portals returned or no longer returned. In this mode, when iscsid starts it will check the discovery db for iSNS records with: discovery.isns.use_discoveryd = Yes This tells iscsi to check for SendTargets discovery records that have the setting: discovery.sendtargets.use_discoveryd = Yes If set, iscsid will perform discovery to the address every discovery.isns.discoveryd_poll_inval or discovery.sendtargets.discoveryd_poll_inval seconds, and it will log into any portals found from the discovery source using the ifaces in /etc/iscsi/ifaces. Note that for iSNS the poll_interval does not have to be set. If not set, iscsid will only perform rediscovery when it gets a SCN from the server. # iSNS Note: # For servers like Microsoft's where they allow SCN registrations, but do not # send SCN events, discovery.isns.poll_interval should be set to a non zero # value to auto discover new targets. This is also useful for servers like # linux-isns (SLES's iSNS server) where it sometimes does not send SCN # events in the proper format, so they may not get handled. Examples -------- SendTargets ----------- - Create a SendTargets record by passing iscsiadm the "-o new" argument in discoverydb mode: iscsiadm -m discoverydb -t st -p 20.15.0.7:3260 -o new On success, this will output something like: New discovery record for [20.15.0.7,3260] added. - Set the use_discoveryd setting for the record: iscsiadm -m discoverydb -t st -p 20.15.0.7:3260 -o update \ -n discovery.sendtargets.use_discoveryd -v Yes - Set the polling interval: iscsiadm -m discoverydb -t st -p 20.15.0.7:3260 -o update \ -n discovery.sendtargets.discoveryd_poll_inval -v 30 To have the new settings take effect, restart iscsid by restarting the iSCSI services. NOTE: When iscsiadm is run with the -o new argument, it will use the discovery.sendtargets.use_discoveryd and discovery.sendtargets.discoveryd_poll_inval settings in iscsid.conf for the records initial settings. So if those are set in iscsid.conf, then you can skip the iscsiadm -o update commands. iSNS ---- - Create an iSNS record by passing iscsiadm the "-o new" argument in discoverydb mode: iscsiadm -m discoverydb -t isns -p 20.15.0.7:3205 -o new Response on success: New discovery record for [20.15.0.7,3205] added. - Set the use_discoveryd setting for the record: iscsiadm -m discoverydb -t isns -p 20.15.0.7:3205 -o update \ -n discovery.isns.use_discoveryd -v Yes - [OPTIONAL: see iSNS note above] Set the polling interval if needed: iscsiadm -m discoverydb -t st -p 20.15.0.7:3205 -o update \ -n discovery.isns.discoveryd_poll_inval -v 30 To have the new settings take effect, restart iscsid by restarting the iscsi services. Note: When iscsiadm is run with the -o new argument, it will use the discovery.isns.use_discoveryd and discovery.isns.discoveryd_poll_inval settings in iscsid.conf for the record's initial settings. So if those are set in iscsid.conf, then you can skip the iscsiadm -o update commands. 8. Advanced Configuration ========================= 8.1 iSCSI settings for dm-multipath =================================== When using dm-multipath, the iSCSI timers should be set so that commands are quickly failed to the dm-multipath layer. For dm-multipath you should then set values like queue if no path, so that IO errors are retried and queued if all paths are failed in the multipath layer. 8.1.1 iSCSI ping/Nop-Out settings ================================= To quickly detect problems in the network, the iSCSI layer will send iSCSI pings (iSCSI NOP-Out requests) to the target. If a NOP-Out times out, the iSCSI layer will respond by failing the connection and starting the replacement_timeout. It will then tell the SCSI layer to stop the device queues so no new IO will be sent to the iSCSI layer and to requeue and retry the commands that were running if possible (see the next section on retrying commands and the replacement_timeout). To control how often a NOP-Out is sent, the following value can be set: node.conn[0].timeo.noop_out_interval = X Where X is in seconds and the default is 10 seconds. To control the timeout for the NOP-Out the noop_out_timeout value can be used: node.conn[0].timeo.noop_out_timeout = X Again X is in seconds and the default is 15 seconds. Normally for these values you can use: node.conn[0].timeo.noop_out_interval = 5 node.conn[0].timeo.noop_out_timeout = 10 If there are a lot of IO error messages like detected conn error (22) in the kernel log then the above values may be too aggressive. You may need to increase the values for your network conditions and workload, or you may need to check your network for possible problems. 8.1.2 SCSI command retries ========================== SCSI disk commands get 5 retries by default. In newer kernels this can be controlled via the sysfs file: /sys/block/$sdX/device/scsi_disk/$host:$bus:$target:LUN/max_retries by writing a integer lower than 5 to reduce retries or setting to -1 for infinite retries. The number of actual retries a command gets may be less than 5 or what is requested in max_retries if the replacement timeout expires. When that timer expires it tells the SCSI layer to fail all new and queued commands. 8.1.3 replacement_timeout ========================= The iSCSI layer timer: node.session.timeo.replacement_timeout = X controls how long to wait for session re-establishment before failing all SCSI commands: 1. commands that have been requeued and awaiting a retry 2. commands that are being operated on by the SCSI layer's error handler 3. all new commands that are queued to the device up to a higher level like multipath, filesystem layer, or to the application. The setting is in seconds. zero means to fail immediately. -1 means an infinite timeout which will wait until iscsid does a relogin, the user runs the iscsiadm logout command or until the node.session.reopen_max limit is hit. When this timer is started, the iSCSI layer will stop new IO from executing and requeue running commands to the Block/SCSI layer. The new and requeued commands will then sit in the Block/SCSI layer queue until the timeout has expired, there is userspace intervention like a iscsiadm logout command, or there is a successful relogin. If the command has run out of retries, the command will be failed instead of being requeued. After this timer has expired iscsid can continue to try to relogin. By default iscsid will continue to try to relogin until there is a successful relogin or until the user runs the iscsiadm logout command. The number of relogin retries is controlled by the Open-iSCSI setting node.session.reopen_max. If that is set too low, iscsid may give up and forcefully logout the session (equivalent to running the iscsiadm logout command on a failed session) before replacement timeout seconds. This will result in all commands being failed at that time. The user would then have to manually relogin. This timer starts when you see the connection error messsage: detected conn error (%d) in the kernel log. The %d will be a integer with the following mappings and meanings: Int Kernel define Description value ------------------------------------------------------------------------------ 1 ISCSI_ERR_DATASN Low level iSCSI protocol error where a data sequence value did not match the expected value. 2 ISCSI_ERR_DATA_OFFSET There was an error where we were asked to read/write past a buffer's length. 3 ISCSI_ERR_MAX_CMDSN Low level iSCSI protocol error where we got an invalid MaxCmdSN value. 4 ISCSI_ERR_EXP_CMDSN Low level iSCSI protocol error where the ExpCmdSN from the target didn't match the expected value. 5 ISCSI_ERR_BAD_OPCODE The iSCSI Target has sent an invalid or unknown opcode. 6 ISCSI_ERR_DATALEN The iSCSI target has send a PDU with a data length that is invalid. 7 ISCSI_ERR_AHSLEN The iSCSI target has sent a PDU with an invalid Additional Header Length. 8 ISCSI_ERR_PROTO The iSCSI target has performed an operation that violated the iSCSI RFC. 9 ISCSI_ERR_LUN The iSCSI target has requested an invalid LUN. 10 ISCSI_ERR_BAD_ITT The iSCSI target has sent an invalid Initiator Task Tag. 11 ISCSI_ERR_CONN_FAILED Generic error that can indicate the transmission of a PDU, like a SCSI cmd or task management function, has timed out. Or, we are not able to transmit a PDU because the network layer has returned an error, or we have detected a network error like a link down. It can sometimes be an error that does not fit the other error codes like a kernel function has returned a failure and there no other way to recovery from it except to try and kill the existing session and relogin. 12 ISCSI_ERR_R2TSN Low level iSCSI protocol error where the R2T sequence numbers to not match. 13 ISCSI_ERR_SESSION_FAILED Unused. 14 ISCSI_ERR_HDR_DGST iSCSI Header Digest error. 15 ISCSI_ERR_DATA_DGST iSCSI Data Digest error. 16 ISCSI_ERR_PARAM_NOT_FOUND Userspace has passed the kernel an unknown setting. 17 ISCSI_ERR_NO_SCSI_CMD The iSCSI target has sent a ITT for an unknown task. 18 ISCSI_ERR_INVALID_HOST The iSCSI Host is no longer present or being removed. 19 ISCSI_ERR_XMIT_FAILED The software iSCSI initiator or cxgb was not able to transmit a PDU becuase of a network layer error. 20 ISCSI_ERR_TCP_CONN_CLOSE The iSCSI target has closed the connection. 21 ISCSI_ERR_SCSI_EH_SESSION_RST The SCSI layer's Error Handler has timed out the SCSI cmd, tried to abort it and possibly tried to send a LUN RESET, and it's now going to drop the session. 22 ISCSI_ERR_NOP_TIMEDOUT An iSCSI Nop as a ping has timed out. 8.1.4 Running Commands, the SCSI Error Handler, and replacement_timeout ======================================================================= Each SCSI command has a timer controlled by: /sys/block/sdX/device/timeout The value is in seconds and the default ranges from 30 - 60 seconds depending on the distro's udev scripts. When a command is sent to the iSCSI layer the timer is started, and when it's returned to the SCSI layer the timer is stopped. This could be for successful completion or due to a retry/requeue due to a conn error like described previously. If a command is retried the timer is reset. When the command timer fires, the SCSI layer will ask the iSCSI layer to abort the command by sending an ABORT_TASK task management request. If the abort is successful the SCSI layer retries the command if it has enough retries left. If the abort times out, the iSCSI layer will report failure to the SCSI layer and will fire a ISCSI_ERR_SCSI_EH_SESSION_RST error. In the logs you will see: detected conn error (21) The ISCSI_ERR_SCSI_EH_SESSION_RST will cause the connection/session to be dropped and the iSCSI layer will start the replacement_timeout operations described in that section. The SCSI layer will then eventually call the iSCSI layer's target/session reset callout which will wait for the replacement timeout to expire, a successful relogin to occur, or for userspace to logout the session. - If the replacement timeout fires, then commands will be failed upwards as described in the replacement timeout section. The SCSI devices will be put into an offline state until iscsid performs a relogin. - If a relogin occurs before the timer fires, commands will be retried if possible. To check if the SCSI error handler is running, iscsiadm can be run as: iscsiadm -m session -P 3 and you will see: Host Number: X State: Recovery To modify the timer that starts the SCSI EH, you can either write directly to the device's sysfs file: echo X > /sys/block/sdX/device/timeout where X is in seconds. Alternatively, on most distros you can modify the udev rule. To modify the udev rule open /etc/udev/rules.d/50-udev.rules, and find the following lines: ACTION=="add", SUBSYSTEM=="scsi" , SYSFS{type}=="0|7|14", \ RUN+="/bin/sh -c 'echo 60 > /sys$$DEVPATH/timeout'" And change the "echo 60" part of the line to the value that you want. The default timeout for normal File System commands is 30 seconds when udev is not being used. If udev is used the default is the above value which is normally 60 seconds. 8.1.4 Optimal replacement_timeout Value ======================================= The default value for replacement_timeout is 120 seconds, but because multipath's queue_if_no_path and no_path_retry setting can prevent IO errors from being propagated to the application, replacement_timeout can be set to a shorter value like 5 to 15 seconds. By setting it lower, pending IO is quickly sent to a new path and executed while the iSCSI layer attempts re-establishment of the session. If all paths end up being failed, then the multipath and device mapper layer will internally queue IO based on the multipath.conf settings, instead of the iSCSI layer. 8.2 iSCSI settings for iSCSI root ================================= When accessing the root partition directly through an iSCSI disk, the iSCSI timers should be set so that iSCSI layer has several chances to try to re-establish a session and so that commands are not quickly requeued to the SCSI layer. Basically you want the opposite of when using dm-multipath. For this setup, you can turn off iSCSI pings by setting: node.conn[0].timeo.noop_out_interval = 0 node.conn[0].timeo.noop_out_timeout = 0 And you can turn the replacement_timer to a very long value: node.session.timeo.replacement_timeout = 86400 9. iSCSI System Info ==================== To get information about the running sessions: including the session and device state, session ids (sid) for session mode, and some of the negotiated parameters, run: iscsiadm -m session -P 2 If you are looking for something shorter, like just the sid to node mapping, run: iscsiadm -m session [-P 0] This will print the list of running sessions with the format: driver [sid] ip:port,target_portal_group_tag targetname Example output of "iscsiadm -m session": tcp [2] 10.15.84.19:3260,2 iqn.1992-08.com.netapp:sn.33615311 tcp [3] 10.15.85.19:3260,3 iqn.1992-08.com.netapp:sn.33615311 To print the hw address info use the -P option with "1": iscsiadm -m session -P 1 This will print the sessions with the following format: Target: targetname Current Portal: portal currently logged into Persistent Portal: portal we would fall back to if we had got redirected during login Iface Transport: driver/transport_name Iface IPaddress: IP address of iface being used Iface HWaddress: HW address used to bind session Iface Netdev: netdev value used to bind session SID: iscsi sysfs session id iSCSI Connection State: iscsi state Note: if an older kernel is being used or if the session is not bound, then the keyword "default" is printed to indicate that the default network behavior is being used. Example output of "iscsiadm -m session -P 1": Target: iqn.1992-08.com.netapp:sn.33615311 Current Portal: 10.15.85.19:3260,3 Persistent Portal: 10.15.85.19:3260,3 Iface Transport: tcp Iface IPaddress: 10.11.14.37 Iface HWaddress: default Iface Netdev: default SID: 7 iSCSI Connection State: LOGGED IN Internal iscsid Session State: NO CHANGE The connection state is currently not available for qla4xxx. To get a HBA/Host view of the session, there is the host mode: iscsiadm -m host This prints the list of iSCSI hosts in the system with the format: driver [hostno] ipaddress,[hwaddress],net_ifacename,initiatorname Example output: cxgb3i: [7] 10.10.15.51,[00:07:43:05:97:07],eth3 To print this info in a more user friendly way, the -P argument can be used: iscsiadm -m host -P 1 Example output: Host Number: 7 State: running Transport: cxgb3i Initiatorname: IPaddress: 10.10.15.51 HWaddress: 00:07:43:05:97:07 Netdev: eth3 Here, you can also see the state of the host. You can also pass in any value from 1 - 4 to print more info, like the sessions running through the host, what ifaces are being used and what devices are accessed through it. To print the info for a specific host, you can pass in the -H argument with the host number: iscsiadm -m host -P 1 -H 7