22.11.2023 13:49, Jonathan Chen wrote: > Hi, > > I'm running a somewhat recent version of STABLE-13/amd64: > stable/13-n256681-0b7939d725ba: Fri Nov 10 08:48:36 NZDT 2023, and I'm seeing > some unusual behaviour with ZFS. > > To reproduce: > 1. one big empty disk, GPT scheme, 1 freebsd-zfs partition. > 2. create a zpool, eg: tank > 3. create 2 sub-filesystems, eg: tank/one, tank/two > 4. fill each sub-filesystem with large files until the pool is ~80% full. In > my case I had 200 10Gb files in each. > 5. in one session run 'md5 tank/one/*' > 6. in another session run 'md5 tank/two/*' > > For most of my runs, one of the sessions against a sub-filesystem will be > starved of I/O, while the other one is performant. > > Is anyone else seeing this?
Please try repeating the test with atime updates disabled: zfs set atime=off tank/one zfs set atime=off tank/two Does it make any difference? Does it make any difference, if you import the pool with readonly=on instead? Writing to ~80% pool is almost always slow for ZFS.
