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).
I don't think you got what I said. Because the controller normally runs as a
RAID controller the controller controls the SATA drives' on-board write
cache, it may not allow the OS to enable/disable the drives' on-board write
cache.
I see what you're saying. I just think that with the BIOS turned off, this
card is essentially acting like a dumb SATA controller, and therefore not
doing anything with the drives' cache.
Using 'dd' to the raw disk will also show the same poor performance if the HD
on-board write-cache is disabled.
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.
Was the 'dd' to the raw disk? Either was it shows the HDs aren't setup
properly.
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
Try using 'format -e' on the drives, go into 'cache' then 'write-cache' and
display the current state. You can try to manually enable it from there.
I tried this, but the 'cache' menu item didn't show up. The man page says
it only works for SCSI disks. Do you know of any other way to get/set
those parameters?
Paul
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