On Jun 21, 2011, at 8:18 AM, Garrett D'Amore wrote: >> >> Does that also go through disksort? Disksort doesn't seem to have any >> concept of priorities (but I haven't looked in detail where it plugs in to >> the whole framework). >> >>> So it might make better sense for ZFS to keep the disk queue depth small >>> for HDDs. >>> -- richard >>> >> > > disksort is much further down than zio priorities... by the time disksort > sees them they have already been sorted in priority order.
Yes, disksort is at sd. So ZFS schedules I/Os, disksort reorders them, and the drive reorders them again. To get the best advantage out of the ZFS priority ordering, I can make an argument to disable disksort and keep the vdev_max_pending low to limit the reordering work done by the drive. I am not convinced that traditional benchmarks show the effects of ZFS priority ordering, though. -- richard _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
