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| author | Zdenek Kabelac <zkabelac@redhat.com> | 2021-01-12 17:59:29 +0100 |
|---|---|---|
| committer | Zdenek Kabelac <zkabelac@redhat.com> | 2021-02-01 12:06:13 +0100 |
| commit | b4212be2e7e8797bbf8f9a166347659cc39ba075 (patch) | |
| tree | b5db3667aa0bcb03d48d793870873d633ea48145 /man | |
| parent | b218a7cfe7179ced64047374af51a883c1611c4d (diff) | |
| download | lvm2-b4212be2e7e8797bbf8f9a166347659cc39ba075.tar.gz | |
thin: improve 16g support for thin pool metadata
Initial support for thin-pool used slightly smaller max size 15.81GiB
for thin-pool metadata. However the real limit later settled at 15.88GiB
(difference is ~64MiB - 16448 4K blocks).
lvm2 could not simply increase the size as it has been using hard cropping
of the loaded metadata device to avoid warnings printing warning of kernel
when the size was bigger (i.e. due to bigger extent_size).
This patch adds the new lvm.conf configurable setting:
allocation/thin_pool_crop_metadata
which defaults to 0 -> no crop of metadata beyond 15.81GiB.
Only user with these sizes of metadata will be affected.
Without cropping lvm2 now limits metadata allocation size to 15.88GiB.
Any space beyond is currently not used by thin-pool target.
Even if i.e. bigger LV is used for metadata via lvconvert,
or allocated bigger because of to large extent size.
With cropping enabled (=1) lvm2 preserves the old limitation
15.81GiB and should allow to work in the evironement with
older lvm2 tools (i.e. older distribution).
Thin-pool metadata with size bigger then 15.81G is now using CROP_METADATA
flag within lvm2 metadata, so older lvm2 recognizes an
incompatible thin-pool and cannot activate such pool!
Users should use uncropped version as it is not suffering
from various issues between thin_repair results and allocated
metadata LV as thin_repair limit is 15.88GiB
Users should use cropping only when really needed!
Patch also better handles resize of thin-pool metadata and prevents resize
beoyond usable size 15.88GiB. Resize beyond 15.81GiB automatically
switches pool to no-crop version. Even with existing bigger thin-pool
metadata command 'lvextend -l+1 vg/pool_tmeta' does the change.
Patch gives better controls 'coverted' metadata LV and
reports less confusing message during conversion.
Patch set also moves the code for updating min/max into pool_manip.c
for better sharing with cache_pool code.
Diffstat (limited to 'man')
| -rw-r--r-- | man/lvmthin.7_main | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/man/lvmthin.7_main b/man/lvmthin.7_main index e6f1d6342..3ce34a5ee 100644 --- a/man/lvmthin.7_main +++ b/man/lvmthin.7_main @@ -1104,7 +1104,7 @@ The default value is shown by: The amount of thin metadata depends on how many blocks are shared between thin LVs (i.e. through snapshots). A thin pool with many snapshots may need a larger metadata LV. Thin pool metadata LV sizes can be from 2MiB -to 16GiB. +to approximately 16GiB. When using lvcreate to create what will become a thin metadata LV, the size is specified with the -L|--size option. @@ -1119,6 +1119,14 @@ needed, so it is recommended to start with a size of 1GiB which should be enough for all practical purposes. A thin pool metadata LV can later be manually or automatically extended if needed. +Configurable setting +.BR lvm.conf (5) +.BR allocation / thin_pool_crop_metadata +gives control over cropping to 15.81GiB to stay backward compatible with older +versions of lvm2. With enabled cropping there can be observed some problems when +using volumes above this size with thin tools (i.e. thin_repair). +Cropping should be enabled only when compatibility is required. + .SS Create a thin snapshot of an external, read only LV |