md3000 performance issues

Christopher McCrory chrismcc at
Wed Jun 6 18:41:28 CDT 2007


Thanks for the responses and updates below

----- "Christopher McCrory" <chrismcc at> wrote:
| Hello...
|   I have found very little tech info on the PV md3000 chassis. All I
| found were 'point and click' type instructions.  My first tests with
| iozone showed that this box screams.  When I put it into production,
| read performance dropped to the floor.  My MD3000 has 8 15k SAS
| drives.
| I tested with raid5 and raid10, both were fast with raid10 being
| slightly faster.


| I suspect the last two changes are the problem and I am going to undo
| them.  Does anyone at Dell have any performance optimization
| documentation?  And/Or real world performance numbers using iozone or
| bonnie?

I ripped out the entire previous config and re-created a raid10 with the 8 15K SAS drives paired in sequence.  No snapshot, no hot spare.  I also updated the BIOS on the 1850 to A06.  The 1850 is running RHEL5 x86_86 6G ram (scsi1 : ioc1: LSISAS1068, FwRev=01060000h:  PCI-X).  The performance is still bad.

 shell> iozone -A -i 0 -s12G
              KB  reclen   write rewrite    read    reread
        12582912       4   83723   55246     3616     3616

As you can see, read performance is a little on the low side.

for comparison, same md3000 on a 2950 with PCI-Express

shell> iozone -A -s 12G
              KB  reclen   write rewrite    read    reread
        12582912       4  169364  160046   224117   231402

Quite a difference...

I'm going to keep poking, but if anyone has any ideas, I'm open for suggestions.

Christopher McCrory
 "The guy that keeps the servers running"

To the optimist, the glass is half full.
To the pessimist, the glass is half empty.
To the engineer, the glass is twice as big as it needs to be.

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