Slow copy performance when using vmWare in conjunction with P4500

[Peter J West]

We currently operate a 6-node P4500 setup which is configured as multisite.  The vast majority of hosts using this SAN are configured in vmWare and on a day-to-day basis we've not seen any major problems.  However, recently we've started migrating mailboxes from an old Exchange 2003 environment into Exchange 2010 and we've noted that the copy process is incredibly slow - typically we're seeing around 0.8GB/hr, whereas doing the same move to local storage yields a throughput of 8gb/hr.

Further to this we also did some tests of copying a 1GB payload file from one location to another.  Copying from a physical Mailbox Server to the SAN was extremely fast, with the process completing in around 3-4 seconds.  However, copying from the physical server to a SAN volume via a Virtualised Server was a much slower process with it taking over 80 seconds to complete the copy.

All this is making me think that the SAN itself is performing ok, but something possibly in the vmWare configuration is leading to very slow copy performance.  Copying the same 1GB file from one volume to another (both SAN-based volumes but exposed to the same Server) also yielded poor results.,

I've tried using both VMDK volumes and volumes accessible via the iSCSI initiator and the performance is roughly equivalent.  I've also tried using the disk shared feature in vmWare to increase performance but it makes next to no difference.

Does anyone have any view on things to check? 

Kind regards

Pete

[Peter J West]

As a test I vMotioned all machines off of one of the ESX hosts and then migrated my 'test Server' onto that host.  I've then set up two VMDK volumes and defined two hard disks.  Again copying a file from one to the other was very slow - the average copy time for a 1GB file was around 70 seconds.

Back to the drawing board......

Pete