Disk write speed is very slow with SAS 6/iR controller

Hello everyone,

All my virtual machines are very slow regarding the disk writing speed .... about 8 MB/sec (The read speed is ok: 65 MB/sec.).

I have two servers with this configuration:

* Dell PowerEdge R610
* 12GB Memory (6x2GB) 1333MHz Dual Ranked UDIMMs
* E5520 Xeon Processor, 2.26GHz 8M Cache, 5.86 GT/s QPI, TurboHT
* ESXi 4 (intalled on a USB Drive)
* Datastore = 2 x 146GB 10K RPM Serial-Attach SCSI 2.5" in RAID 1 (SAS 6/iR Integrated Controler)
* 4 VM's running (2 x Windows 2003 Server x64 / Windows 2003 Server x32 / Windows 2008 WebServer x32) VM Controller: LSI Logic Parallel

The 2 servers (all virtual machine) have the same problem (Disk Write Speed = 8MB/sec. for all VMs). It's very slow.

This SAS6/iR controller does not have a battery on board to handle cached writes during an unexpected power outage, so enabling write caching is not a solution for me.

I found that the Dell SAS6/iR is basically a re-branded LSI 1068E ( http://communities.vmware.com/message/1327115#1327115 ) and it's supposed to be supported by vmware.

I found also that another person seem to have the same problem with the LSISAS1068 ( http://communities.vmware.com/thread/114158 )

Any ideas ?? Does other people experience the same problem ?

Thanks