To me it does not look like a RAID problem per se. 53 4327 70564 74.9 131.3 5.9 47.3 83.9 54 4327 35282 74.9 50.7 6.6 13.8 36.8 55 4327 35282 74.9 70.0 5.6 22.0 47.9 I think, in this configuration the problem is because there is a significant imbalance in unit size. Unit 53 is twice the size of other two. Having set aside potential hot spots, normally I/O load is spread proportionally to amount of data stored on the drive, which again is roughly proportional to disk size. As a result, unit 53 has to handle twice the load. If I/O load is light, this is not an issue, but with heavy load this unit will be simply overloaded. RAID configurations are always somewhat unbalanced in size, but usually not so much (25% on 4-unit set, 12.5% on 8-unit set). This configuration is simply not for heavy disk workload. You will have to frequently rebalance data to keep data allocation "skewed" to compensate for disk size imbalance. Adding one drive to the RAID set will make all drives equal in size, which is very very importnat for disk performance under heavy load. Alexei Pytel always speaking for myself only Where is the beginning of the end, which ends the beginning? rob@xxxxxxxxx Sent by: midrange-l-bounces+pytel=us.ibm.com@xxxxxxxxxxxx 10/01/2004 04:10 PM Please respond to Midrange Systems Technical Discussion To midrange-l@xxxxxxxxxxxx cc Subject Three drive raid set. Anyone else out there have serious performance issues with a three drive raid set? We are. And we even ran STRASPBAL. IBM tried iDoctor, etc. Nothing out of the ordinary. So, their suggestion is a STRASPBAL *ENDALC and then add them back in with STRASPBAL *CAPACITY. Our BP says he knows of another customer that had the same issue but just ordered another drive and it was solved. Never opened pmr with IBM. Trying to find a few "me too's", hopefully with pmr #'s, to encourage IBM to look harder. We will buy more drives. We were hoping to put it off awhile. Boss does think that getting them in before year end is a good thing though, budgetwise. System ASP . . . . . . . : 3316 G % system ASP used . . . : 74.9333 WRKDSKSTS Size % I/O Request Read Write Unit Type (M) Used Rqs Size (K) Rqs Rqs ... 50 4327 52923 74.9 15.3 8.6 7.0 8.2 51 4327 70564 74.9 25.3 7.9 13.7 11.6 52 4327 61744 74.9 29.4 6.4 17.7 11.6 53 4327 70564 74.9 131.3 5.9 47.3 83.9 54 4327 35282 74.9 50.7 6.6 13.8 36.8 55 4327 35282 74.9 70.0 5.6 22.0 47.9 The last three are the raid set in question. Rob Berendt -- Group Dekko Services, LLC Dept 01.073 PO Box 2000 Dock 108 6928N 400E Kendallville, IN 46755 http://www.dekko.com -- This is the Midrange Systems Technical Discussion (MIDRANGE-L) mailing list To post a message email: MIDRANGE-L@xxxxxxxxxxxx To subscribe, unsubscribe, or change list options, visit: http://lists.midrange.com/mailman/listinfo/midrange-l or email: MIDRANGE-L-request@xxxxxxxxxxxx Before posting, please take a moment to review the archives at http://archive.midrange.com/midrange-l.
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