On Sep 27, 2009, at 1:44 PM, Paul Archer <p...@paularcher.org> wrote:
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.
You are probably right that the controller doesn't do anything,
neither enables or disables the drives' cache, so whatever they were
set to before it was switched to JBOD mode is what they are now.
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?
Hmm, I thought SATA under Solaris behaves like SCSI? I use RAID
controllers that export as each-disk-raid0 which uses the SCSI command
set so it abstracts the SATA disks, so I have no way to verify myself.
-Ross
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