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. Thanks, Jorge
