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| author | Colin Walters <walters@verbum.org> | 2011-10-17 11:08:25 -0400 |
|---|---|---|
| committer | Colin Walters <walters@verbum.org> | 2011-10-17 11:08:25 -0400 |
| commit | aaae116f8e60b3c563c8f6b8b1616ceb938517ce (patch) | |
| tree | 35a643a63e7bdb856c01619d1dba60b37043ec49 /README.md | |
| parent | 8020f444cf7bbc936be9e45670401e641e297d36 (diff) | |
| download | ostree-aaae116f8e60b3c563c8f6b8b1616ceb938517ce.tar.gz | |
README: Some notes on BTRFS
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| -rw-r--r-- | README.md | 35 |
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@@ -325,6 +325,37 @@ harder would be maintaining binary compatibilty with any arbitrary Note these RPMs act like local configuration - they would be reinstalled every time you switch roots. +What about BTRFS? Doesn't it solve everything? +----------------------------------------------- + +In short, BTRFS is not a magic bullet, but yes - it helps +significantly. The obvious thing to do is layer BTRFS under dpkg/rpm, +and have a separate subvolume for /home so rollbacks don't lose your +data. See e.g. +<http://fedoraproject.org/wiki/Features/SystemRollbackWithBtrfs> + +As a general rule an issue with the BTRFS is that it can't roll back +just changes to things installed by RPM (i.e. what's in rpm -qal). + +For example, it's possible to e.g. run yum update, then edit something +in /etc, reboot and notice things are broken, then roll back and have +silently lost your changes to /etc. + +Another example is adding a new binary in /usr/local. You could say, +"OK, we'll use subvolumes for those!". But then what about /var (and +your VM images that live in /var/lib/libvirt ?) + +Finally, probably the biggest disadvantage of the rpm/dpkg + BTRFS +approach is it doesn't solve the race conditions that happen when +unpacking packages into the live system. This problem is really +important to me. + +Note though hacktree can definitely take advantage of BTRFS features! +In particular, we could use "reflink" +<http://lwn.net/Articles/331808/> instead of hard links, and avoid +having the object store corrupted if somehow the files are modified +directly. + Other systems ------------- @@ -355,6 +386,10 @@ didn't use them: bad, but hacktree is better than it for the exact same reasons git is better than Subversion. + - BTRFS: <http://en.wikipedia.org/wiki/Btrfs> + + See above. + - Jhbuild: <https://live.gnome.org/Jhbuild> What we've been using in GNOME, and has the essential property of allowing you |