On 15/02/2012, at 8:00 PM, Tim Connors wrote:
It's not ready yet. I installed 3.2 (can't get terribly much more modern by installing debian kernel packages), made a several hundred gig btrfs filesystem and chucked half of several hundred gig onto it. 3 oops with btrfs traces later, I decided I'd remake the FS as ext4.
There have been a lot of stability fixes in 3.3 and 3.4. Are you reporting these oops' anywhere? Obviously this is very important to me, as Release Manager for Oracle Linux's UEK2 and btrfs. :) Our internal QA testing is seriously hammering btrfs at the moment, so I'd be interested to know if you can reproduce these issues. If you can, please email me directly with the steps to reproduce so that I can try and get Oracle QA to try it as well.
I also worry about the really bad fragmentation of files. Sounds like a fundamental problem if you want to have writes that are friendly to SSD, you're going to have reads that are very much unfriendly to spinning rust.
btrfs includes both scrubbing and balancing routines, and we recommend you scrub on a regular basis for any multi-device btrfs volume. It also does automatic and online defragmentation. btrfs also adjusts itself for SSD vs spinning rust, which you can tune via mount options (i.e. if it detects something as spinning when it's not or vice-versa).
Gee, given the filesystem pain we already have on our rhel and oel boxen, I'm sure I'd excite my colleagues by suggesting we stick with the New Shiny! defaults!
While we will support btrfs in production, we don't expect customers to rush to convert all their boxes on the day of release. :) Hell, I still have customers on OL3 running Oracle 9i, so just getting them to OL5 would be a start. However, for those customers that do want the benefit of the latest filesystem functionality, we will support btrfs on OL5 and OL6 when we release UEK2. Obviously the biggest benefit for enterprise customers initially is the filesystem snapshot functionality, especially when you use the yum-plugin-fs-snapshot: btrfs will automatically create a snapshot of the filesystem prior to any package installation/upgrade, so in the event of a failure, you can just reboot into a known good state. When you combine the snapshot capabilities of btrfs with our rebootless kernel patching via K-splice, along with the addition of Clusterware and OCFS2, Oracle Linux really does provide some excellent enterprise-grade resilience that is unavailable from any other vendor. Cheers, Avi