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)
Edited by powerhouse, 07 November 2010 - 12:58 AM.