On 2019/11/27 下午11:11, Jorge Bastos wrote: > I believe this is a known issue but wonder if there's something I can > do do optimize raid5 scrub speed, or if anything is in the works to > improve it. > > kernel 5.3.8 > btrfs-progs 5.3.1 > > > Single disk filesystem is performing as expected: > > UUID: 9c0ed213-d9c5-4e93-b9db-218b43533c15 > Scrub started: Tue Nov 26 21:58:20 2019 > Status: finished > Duration: 2:24:32 > Total to scrub: 1.04TiB > Rate: 125.17MiB/s > Error summary: no errors found > > > > 4 disk raid5 (raid1 metadata) on the same server using the same model > disks as above: > > UUID: b75ee8b5-ae1c-4395-aa39-bebf10993057 > Scrub started: Wed Nov 27 07:32:46 2019 > Status: running > Duration: 7:34:50 > Time left: 1:52:37 > ETA: Wed Nov 27 17:00:18 2019 > Total to scrub: 1.20TiB > Bytes scrubbed: 982.05GiB > Rate: 36.85MiB/s > Error summary: no errors found > > > > 6 SSD raid5 (raid1 metadata) also on the same server, still slow for > SSDs but at least scrub performance is acceptable: > > UUID: e072aa60-33e2-4756-8496-c58cd8ba6053 > Scrub started: Wed Nov 27 15:08:31 2019 > Status: running > Duration: 0:01:40 > Time left: 1:40:11 > ETA: Wed Nov 27 16:50:24 2019 > Total to scrub: 3.24TiB > Bytes scrubbed: 54.37GiB > Rate: 556.73MiB/s > Error summary: no errors found > > I still have some reservations about btrfs raid5/6, so use mostly for > smaller filesystems for now, but this slow scrub performance will > result in multi-day scrubs for a large filesystem, which isn't very > practical. Btrfs uses a not-so-optimal way for multi-disks scrub: Queuing scrub for each disk at the same time. So it's common to cause a lot of race and even conflicting seek requests. Have you tried to only scrub one disk for such case? Thanks, Qu > > Thanks, > Jorge >
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