btrfs requirements for Quantal

Registered by Colin Watson on 2012-05-03

Catch up with significant btrfs consumers (particularly the server team) on their requirements for btrfs in Quantal, in light of upstream activity. Figure out areas where we might be able to help.

Blueprint information

Status:
Not started
Approver:
Steve Langasek
Priority:
Low
Drafter:
Dimitri John Ledkov
Direction:
Approved
Assignee:
Dimitri John Ledkov
Definition:
Approved
Series goal:
Accepted for raring
Implementation:
Not started
Milestone target:
milestone icon ubuntu-13.04-beta-1

Whiteboard

Dump of notes from UDS-Q Etherpad.

* loads of btrfs benchmarks done
 * tends to fragment write heavy loads
 * snapshots are good for the upgrade testing ^W^W^W everything
   - we have the apt-brtfs-snapshot package that we would like to use
   - and nexentra did something similar with zfs
 * a lot of space is 'reserved' for COW behaviours, knowing how much space is available is hard
 * we are doing an fsck on every boot, and it is not doing a good job either
  - fsck should not be installed as it will be used automatically if it is not going to do a good job
 * are the server still wanting this for CEPHs?
 * grub2 has btrfs support, we can boot.
  - but it is missing write support for things like 'last boot failed' -- work is designed for this
          ^ hence the " There's still that stupid message on boot "Sparse file not allowed" "
* ureadahead with btrfs?
* fedora might get it as default (wait and see)
* good for fast installation
   - move filesystem across & resize = full install in minutes
   - needs info & link to why this is the case
* hard-link limit is small for use-cases like bacula, mutt (256 in one dir? http://john.freml.in/btrfs-hard-links-limit wikipedia reports more; no reported limit for all links to one file that I have found)
* no fully implemented quota support (needs checking)

= links =
* Fsck implementation of btrfs ( "dangerdonteveruse" )
http://www.phoronix.com/scan.php?page=news_item&px=MTA2MDI
* Anyone has the link to the recent btrfs benchmarks?
btrfs on 12.04 - http://www.phoronix.com/vr.php?view=17164
various mount options - http://www.phoronix.com/vr.php?view=17187
xfs linux conf.au presentation that has some comparisions with btrfs
- paper http://xfs.org/index.php/Image:Xfs-scalability-lca2012.pdf
- video http://www.youtube.com/watch?v=FegjLbCnoBw

benchmarks: http://zinc.canonical.com/~cking/fs-test
http://btrfs.boxacle.net/

video: http://vimeo.com/15325851

https://help.ubuntu.com/community/btrfs
https://wiki.ubuntu.com/FoundationsTeam/BtrfsSupport

XFS filesystem of the future (?!) https://lwn.net/Articles/476263/

Quickly browsing cephs mailing list on gmane reveals:
* there are btrfs devs and emails cross posted to btrfs mailing list (healthy relationship)
* there are ongoing tests of using btrfs
* latest thread about ceph on top of btrfs from 3.4rc reveals btrfs bugs/warnings: http://news.gmane.org/find-root.php?group=gmane.comp.file-systems.ceph.devel&article=6082
* this means that probably btrfs is not good/recommended option for running ceph in production
* further pings needed

(?)

Work Items

Work items:
engage kernel/qa/iso testing on btrfs ongoing testing: TODO
setup a precise->quantal btrfs based upgrade test in the QA lab (blocked on UTAH development): BLOCKED
document caveats, benchmarks, missing features, errors (nothing obvious is missing from https://help.ubuntu.com/community/btrfs): DONE
publicize btrfs usage to powerusers (jorge did a block post during quantal?! cycle): DONE
look at grub2 write to boot area linked as a bug report instead bug #736743: POSTPONED
investigate if btrfs is recommended for CEPH (probably not): DONE