I am running a Dual Xeon (2x X5650 Westmere CPUs) config. with 12GB DDR3 ECC 1333MHz and a 450GB SAS Seagate Cheetah 15.7K (15000rpm) HDD on a LSI SAS 9260-8i raid controller.
The HDD sits in a Raid0 configuration (there is no second drive, kind of like JBOD) with following settings enabled in the controller:
Read-ahead enabled, disk cache enabled, I/O access: direct, write-back (no BBU unit/I don't have one yet), stripe size 64K.
My problem is that when I copy a large file (i.e. 2GB) it jumps to the middle of the process in one second then there's a sudden drop in transfer speed (below 50MBps) and keeps dropping making large file transfers a pain.
I have run a HD Tune test and I get the following: 119MBps minimum, 196MBps maximum, 167MBps average - this is with a 256K stripe (not 64K)
Also worth mentioning, the HDD connects to a 3Gbps backplane - the SAS controller and HDDs are both SAS2 (6GBps). I know the backplane is a bottleneck but shouldn't I at least have steady transfer rates not dropping below 50MBps and craps out completely?
And another question? Is this because I have a single drive in the Raid0 configuration? Could it be because the controller is writing the same stuff twice onto the same drive? (that's my theory)
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This post has been edited by powerhouse: 07 November 2010 - 12:58 AM