performance tuning on perc6 (LSI) controller

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performance tuning on perc6 (LSI) controller

Benjeman J. Meekhof
Should clarify that the first test mentioned below used the same gstripe
setup as the latter one but did not specify any newfs blocksize:

#gstripe label -v -s 128k test /dev/mfid0 /dev/mfid2
#newfs -U /dev/stripe/test



I think this might be useful information, and am also hoping for a
little input.

We've been doing some FreeBSD benchmarking on Dell PE2950 systems with
Perc6 controllers (dual-quad Xeon, 16GB, Perc6=LSI card, mfi driver,
7.0-RELEASE).  There are two controllers in each system, and each has
two MD1000 disk shelves attached via the 2 4x SAS interfaces.  (so 30PD
available to each controller, 60 PD on the system).

My baseline was this - on linux 2.6.20 we're doing 800MB/s write and
greater read with this configuration:  2 raid6 volumes volumes striped
into a raid0 volume using linux software raid, XFS filesystem.  Each
raid6 is a volume on one controller using 30 PD.  We've spent time
tuning this, more than I have with FreeBSD so far.

Initially I was getting strangely poor read results.  Here is one
example (before launching into quicker dd tests, i already had similarly
bad results from some more complete iozone tests):

time dd if=/dev/zero of=/test/deletafile bs=1M count=10240
10737418240 bytes transferred in 26.473629 secs (405589209 bytes/sec)
  time dd if=/test/deletafile of=/dev/null bs=1M count=10240
10737418240 bytes transferred in 157.700367 secs (68087465 bytes/sec)

To make a very long story short, much better results achieved in the end
by simply by increasing the filesystem blocksize to the maximum (same dd
commands).  I'm running a more thorough test on this setup using iozone:

#gstripe label -v -s 128k test /dev/mfid0 /dev/mfid2
#newfs -U -b 65536 /dev/stripe/test

#write:  19.240875 secs (558052492 bytes/sec)
#read:  20.000606 secs (536854644 bytes/sec)

Also did this in /boot/loader.conf - it effected nothing very much in
any test but the settings seemed reasonable so I kept them:

Any other suggestions to get best throughput?  There is also HW RAID
stripe size to adjust larger or smaller.  ZFS is also on the list for
testing.  Should I perhaps be running -CURRENT or -STABLE to be get best
results with ZFS?


Benjeman Meekhof - UM ATLAS/AGLT2 Computing
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