[Lustre-discuss] Not sure how we should configure our RAID arrays (HW limitation)

[Kevin Van Maren]

The 512K stripe size should be fine for Lustre, and 128KB per disk is enough to get good performance from the underlying hard drive.

I don't know anything about the E18s beyond what you've posted, so I can't guess which configuration is more optimal, so I would suggest you create the RAID arrays, format the LUNs for Lustre, and run the Lustre iokit and see how the various configurations perform (3 * 4+2, 2 * 8+1, 2 * 7+2).  Then please post results (with mkfs, etc command lines) here so others can benefit from your experiments and/or suggest additional tunings.

Kevin


On May 4, 2012, at 3:14 PM, Frank Riley wrote:

>> How about doing 3 4+2 RAIDs?  12 usable disks, instead of 14 or 16, but still
>> better than 8 with RAID1.  Doing 4*128KB, resulting in 2 full-stripe writes for
>> each 1MB IO is not that bad.
> 
> Yes, of course. I had thought of this option earlier but forgot to include it. Thanks for reminding me. So using a stripe width of 512K will not harm performance that much? Note also that the E18s have two active/active controllers in them so that means one controller will be handling I/O requests for 2 arrays, which will reduce performance somewhat. Would this affect your decision between 3 4+2 (512K) or 2 7+2 (896K)?
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