Hi there,
I have similar problems, but am using IBM X3755 M3 4 socket servers, Citrix Xenserver, Cisco MDS 9148 and Netapp FAS 2240-2 in active active controller.
I have another Xenserver in the lab with SATA drives on a raid controller with BBWC and I have better performance there than on the netapp!
I have bad read performance in the virtual machine and on database cluster.
I have since discovered that the Netapp FAS 2240-2 does not have any cache. No read Cache, no write cache. The models higher up, do.
I have decided to implement another shelf, extend the aggregate with the same disks, and put 4x200GB SSD disks for the flex pool.
Hopefully, this will help.
Regards
Stavros