Problem is that while it's back, the performance is horrible. It's
resilvering at about (according to iostat) 3.5MB/sec. And at some point, I
was zeroing out the drive (with 'dd if=/dev/zero of=/dev/dsk/c7d0'), and
iostat showed me that the drive was only writing at around 3.5MB/sec. *And*
it showed reads of about the same 3.5MB/sec even during the dd.
This same hardware and even the same zpool have been run under linux with
zfs-fuse and BSD, and with BSD at least, performance was much better. A
complete resilver under BSD took 6 hours. Right now zpool is estimating
this resilver to take 36.
Could this be a driver problem? Something to do with the fact that this is
a very old SATA card (LSI 150-6)?
This is driving me crazy. I finally got my zpool working under Solaris so
I'd have some stability, and I've got no performance.
It appears your controller is preventing ZFS from enabling write cache.
I'm not familiar with that model. You will need to find a way to enable the
drives write cache manually.
My controller, while normally a full RAID controller, has had its BIOS
turned off, so it's acting as a simple SATA controller. Plus, I'm seeing
this same slow performance with dd, not just with ZFS. And I wouldn't
think that write caching would make a difference with using dd (especially
writing in from /dev/zero).
The other thing that's weird is the writes. I am seeing writes in that
3.5MB/sec range during the resilver, *and* I was seeing the same thing
during the dd.
This is from the resilver, but again, the dd was similar. c7d0 is the
device in question:
r/s w/s kr/s kw/s wait actv wsvc_t asvc_t %w %b device
0.0 238.0 0.0 476.0 0.0 1.0 0.0 4.1 0 99 c12d1
30.8 37.8 3302.4 3407.2 14.1 2.0 206.0 29.2 100 100 c7d0
80.4 0.0 3417.6 0.0 0.3 0.3 3.3 3.2 8 14 c8d0
80.4 0.0 3417.6 0.0 0.3 0.3 3.4 3.2 9 14 c9d0
80.6 0.0 3417.6 0.0 0.3 0.3 3.4 3.2 9 14 c10d0
80.6 0.0 3417.6 0.0 0.3 0.3 3.3 3.1 9 14 c11d0
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0 0 c12t0d0
Paul Archer
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