Benching RAID and AX100 vs. single SCSI disk - weird results

Dmitriy Beloslyudtsev beloslyu1 at gmail.com
Tue Mar 22 12:05:58 CST 2005


Hi!
Have you seeing this tuning recommendation from qlogic?
http://download.qlogic.com/drivers/26274/QLogic_Linux.pdf
They suggest some tuning and versions of qlogic drivers to use.

Hope it helps.

Dima

On Tue, 22 Mar 2005 09:37:17 -0600, Fran Fabrizio <fran at cis.uab.edu> wrote:
> 
> I'm currently evaluating an AX100 for purchase.  I hooked up the AX100
> to a RHEL3 PE1750 with a QLogic qla200 HBA directly (so, In a DAS
> configuration).  I created a single LUN, a RAID5 partition across the 4
> 250GB SATA disks that are in the AX100 currently, and formatted it as
> ext3 (most of the things I will compare it to also have ext3).  I ran
> some Bonnie++ benchmarks on it vs. a single SCSI disk and some other
> RAID configurations I have on my network.  I saw some very surprising
> (to me, anyway) results:
> 
> - The single SCSI disk outperforms all of the RAID solutions in most
> categories
> - I saw some really weird results where a 3-disk RAID5 on a PERC blew
> away every other solution on file creates/deletes per second
> - Under load (4 concurrent Bonnie++ instances), the AX100 degraded as
> much as a single SCSI disk (contrary to what our Dell tech rep was
> expecting to see)
> 
> In general, I'm surprised that RAID in all of the various configurations
> I have cannot outperform a single disk (particularly for reading).
> Also, I'm surprised that the AX100 is playing in the same ballpark as
> other RAIDs and even NFS for some tests, whereas I was expecting better
> performance from it.
> 
> Some people who have already seen my results have said that it might be
> due to Dell RAID controllers being slow, and I've definitely heard that
> chatter on this list in the past.  However, I think there's something
> more going on (such as the AX100 is misconfigured, or I have
> unreasonable expectations of RAID and the AX100).
> 
> Anyhow, my results are at http://www.cis.uab.edu/fran/ax100-3-21.pdf
> 
> Page 1 - a single Bonnie++ run
> Page 2 - single run but with OS buffering disabled (forces an fsync
> after each I/O)
> Page 3 - 4 concurrent runs (only AX100 vs. local single SCSI disk,
> because we were expecting to see the AX100 handle it better than the
> local disk, but nope)
> Page 4 - some notes on the different storage systems I tested and how I
> ran Bonnie++
> 
> Any and all thoughts as to how to explain what I am seeing would be much
> appreciated.




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