Hi all,

I encounter some performance problems when accessing LUNs from Linux app servers running SLES10 & 11 and mainly with CentOS 5.4 (RedHat).

Setup: Datacore SANmelody 2 PSP4 u4 with HA. Pools are with 4MB and 128MB SU size. Tests are made with IOmeter. One vvol created from each pool. The vvols, which are linear, would be presented to Windows 2008 or the Linux boxes to get the performance values, but one ofter one, and all is used directly (raw), without any file system. FC cards are Emulex 11002 connected over Brocade 200 or 4900 running FAB OS 5.3.0d or 6.2.

The first thing I found out is, that the performance will improve when used 128MB SU size instead the 4MB for the Linux machines, but not for Windows.

When I run the IOmeter (with smaller block sizes like 512 B up to 8 KB) on the Windows 2008 and take this as a base line with 100%, and then start the same thing on the Linux side, I got around 25% on the CentOS up to 30% on the SLES11 boxes. When using larger block sizes, it goes up to 50%, but never up to the same or around the performnce that the WIndows get.

My thougths are, that the Linux has some problems accessing the SANmelody. I tried to set the read ahead values to some higher values via blockdef --setra, but this does not help.

How could I change, e.g., the HBA settings used by the CentOS 5.4, or what to change?

Any other ideas?

Any kind of information or suggestions are appreciated.

Best regards

Dunkan