Disk write speed is very slow with Dell SAS 6/iR c...

steph22 · ‎09-30-2009

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:

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.

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

LucasAlbers · ‎09-30-2009

hmm.

Enable write cache in the bios.

Verify your bios options are set correctly.

Run your system with memory interleaving enabled so it can run in numa mode.

You should consider adding two more disks so you can run in raid 10, this has better reliability and write performance.

steph22 · ‎10-01-2009

Thanks, but unfortunately the 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.

LucasAlbers · ‎10-01-2009

I have a 610 and by default it has a battery back cache.

You have to specifically tell it to run with a writeback cache if you don't have a battry.

See the dell documentation.

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