aac scsi raid driver performance

[Scott Long]

Turn off read caching

Ahnjoan Amous wrote:
> I reset the controller to the defaults for everything before I did the
> installation.
> 
> Each of the containers were created with the following options.
> Container Type - RAID 0
> Container Label - data03
> Container Size - 279.396 GB
> Chunk Size - 64KB
> Read Caching (Yes/No) - Y
> Write Caching : Enable when protected
> Create RAID 5 via - N/A
> 
> Then the controller itself has a single cache option
> Drives Write Cache - Disabled
> 
> Thanks
> Ahnjoan
> 
> On 1/11/07, Scott Long <scottl at samsco.org> wrote:
>> Did you enable read caching for the arrays?
>>
>> Scott
>>
>>
>> Ahnjoan Amous wrote:
>> > I'm trying to find possible explanations for slow concurrent writes
>> > through the
>> > aac driver.  This machine runs under 1% load and has less than 4
>> > transfers per
>> > second to the drives in question when not being used for testing.
>> >
>> > When I attempt sequential "dd"s as follow, the results are better then
>> > 70MB/sec.
>> >  dd if=/dev/zero of=/data02/helloworld bs=1m count=1000
>> >    1048576000 bytes transferred in 13.886718 secs (75509274 bytes/sec)
>> >  dd if=/dev/zero of=/data03/helloworld bs=1m count=1000
>> >    1048576000 bytes transferred in 14.011323 secs (74837758 bytes/sec)
>> >
>> > When I attempt concurrent "dd"s as follow, with a 1 second sleep
>> interval
>> > between starts, the results are better than 40MB/sec
>> >  dd if=/dev/zero of=/data02/helloworld bs=1m count=1000 &
>> >  sleep 1
>> >  dd if=/dev/zero of=/data03/helloworld bs=1m count=1000 &
>> >    1048576000 bytes transferred in 25.269555 secs (41495626 bytes/sec)
>> >    1048576000 bytes transferred in 24.935765 secs (42051086 bytes/sec)
>> >
>> > When I attempt concurrent "dd"s as follow, the results are little
>> better
>> > than
>> > 20MB/sec
>> >  dd if=/dev/zero of=/data02/helloworld bs=1m count=1000 &
>> >  dd if=/dev/zero of=/data03/helloworld bs=1m count=1000 &
>> >    1048576000 bytes transferred in 44.963408 secs (23320652 bytes/sec)
>> >    1048576000 bytes transferred in 45.010065 secs (23296478 bytes/sec)
>> >
>> > I can't account for what causes the huge difference however the
>> results are
>> > reproducible.  I've run the tests dozens and dozens of times now, first
>> > blaming
>> > the em driver for my slow ggatec/ggated results, then GEOM for my slow
>> > local
>> > mirroring after eliminating the network, and finally blaming the aac
>> driver
>> > after removing GEOM from the equation.  If anyone has ideas on what
>> I might
>> > look at or change or test I would love to hear.
>> >
>> >
>> > ****** Misc. Information ******
>> > root:somehost:~ > df -k
>> > Filesystem    1K-blocks    Used  Avail Capacity  Mounted on
>> > /dev/aacd2s1e   2026030 1024532 839416    55%    /data02
>> > /dev/aacd3s1e   2026030 1024532 839416    55%    /data03
>> > Hardware -
>> > aac - Dell PERC3/Di U160
>> > aacd2 - hardware RAID 0, w/1 U320 300G drive
>> > aacd3 - hardware RAID 0, w/1 U320 300G drive
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