I have a brand new Dell VRTX box set up as a Failover Cluster running HA Hyper-V virtual machines. This is my first time setting up clustering, and my first time with one of these boxes, so I'm sure I've missed something.

The virtual machines are experiencing high disk latency and bad performance when accessing their VHD(x) files located on a Cluster Shared Volume.

The VRTX has 10 x 900 GB 10K SAS drives in RAID 6 configuration, and the VRTX has the redundant Shared PERC 8 controllers. Both blades have full access to the virtual disks. There are two M520 blades installed, each with 128 GB RAM. MPIO is configured for the PERC 8 controllers. Operating system on the blades is Server 2012 (NOT R2).

The RAID 6 array is split into a small (8 GB) volume for cluster quorum witness and a large (6.5 TB) volume for a Cluster Shared Volume (mounted on the nodes as C:\ClusterStorage\Volume1)

An example of slow disk access: logging into a Server 2012 VM and having Server Manager come up automatically. Disk access goes to 100%, with write speeds at 20 MB or so, read speeds of 500 KB or so, and Average Response Time of over 1000 ms, sometimes spiking at 4000-5000 ms or so. It's the latency that really worries me.

Is there something specific I should look at in my configuration? It doesn't seem to matter whether I use VHD or VHDX, dynamic or static.