About a year ago I was talking to j On 01/30/2015 07:24 AM, Luke Kao wrote:
Dear ceph users, Has anyone tried to add autodefrag and mount option when use btrfs as the osd storage?
Sort of. About a year ago I was looking into it, but Josef told me not to use either defrag or autodefrag. (especially when lots of snapshots are used) There is/was a bug that can make the box go OOM and keel over. I think fixing it was on the roadmap but I haven't heard if anything ever made it in.
In some previous discussion that btrfs osd startup becomes very slow after used for some time, just thinking about add autodefrag will help. We will add on our test cluster first to see if there is any difference. Please kindly share experience if available, thanks
With OSDs on BTRFS, we saw better performance across the board vs XFS initially on a fresh deploy. After ~30 minutes of small random writes to RBD volumes, everything got incredibly fragmented and sequential reads degraded by about 200%. Presumably this is due to COW. Even if defrag was safe, there'd be a lot of data to clean up...
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