On Mon, Apr 24, 2023 at 1:25 PM Carlos Carvalho <carlos@xxxxxxxxxxxxxx> wrote:
>
> Jan Kara (jack@xxxxxxx) wrote on Mon, Apr 17, 2023 at 02:15:37PM -03:
> > Commit 7e55c60acfbb ("md/raid5: Pivot raid5_make_request()") changed the
> > order in which requests for underlying disks are created.
>
> In which version was this first applied?
7e55c60acfbb ("md/raid5: Pivot raid5_make_request()") is in 6.0+ kernels.
>
> We've observed a large drop in disk performance since 4.* to the point that
> 6.1.* is almost unusable for some tasks. For example, we have 2 backup
> machines, one using raid6/ext4 and another using zfs. The backup of a third
> machine with a filesystem with ~25M inodes takes 6x-8x longer on the one using
> raid6/ext4 than on the one using zfs... This is during the rsync phase.
> Afterwards it removes old trees and the rm with raid6 takes eons even though
> the disks are not at all busy (as shown by sar). Running several rm in parallel
> speeds things up a lot, showing the problem is not in the disks.
I am hoping to look into raid performance soon. But I cannot promise anything
at the moment.
Thanks,
Song
