The most important information from the Wednesday session entitled "btrfs requirements for Quantal" is that EXT4 will continue to be the default file-system for Ubuntu 12.10. Btrfs has long been available as an install-time alternative for Btrfs, but with the Quantal release they will not yet be moving to Btrfs by default.
Ubuntu developers still aren't confident in Btrfs due to the repair tool being questionable, Fedora not yet defaulting to Btrfs (this might happen in F18), and just all around not feeling like its ready. As Fedora 18 won't be due until November, assuming the Btrfs default switch happens then, Canonical would certainly like to see the feedback from that release and for any upstream Btrfs fixes from Red Hat before migrating from EXT4. With that said, it could maybe by a possibility for Ubuntu 13.04 but I suspect that if the switch happens it wouldn't occur until Ubuntu 13.10.
Below are the officially recorded notes for the Btrfs session for those without an Ubuntu sign-on to view them here.
* 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" )
* 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
== ACTIONS ==
[???] communicate with server about CEPHs underlying filesystem recommnedations choices
try to get more testing & get more user using it (Advertise & Experiment)
setup a precise->quantal btrfs based upgrade test in the QA lab?
engage kernel/qa testing on btrfs ongoing testing
look at grub2 write to boot area