aac scsi raid driver performance

[Scott Long]

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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