The storage consists of separate RAID arrays with high speed discs for Data (4 discs RAID10), Logs (2 discs RAID1), Quorum and MSDTC (2 discs RAID1). The nodes are virtual and each runs on a separate ESX host. These are both connected to the storage via a fibre channel. Both nodes map to the same RDMs and the server's local discs (I.E. C: drives) also exist on the same data store.

That's about as far as my knowledge of the storage goes I'm afraid...!

I ran SQLIO on both nodes and got the following results, which just confirms my suspicions:

NODE 1 (Problem Node):

Writes using 8KB random IOs - IOs/sec: 971.79 MBs/sec: 7.59

Reads using 8KB random IOs - IOs/sec: 887.03 MBs/sec: 6.92

Writes using 64KB sequential IOs - IOs/sec: 157.00 MBs/sec: 9.81

Reads using 64KB sequential IOs - IOs/sec: 154.86 MBs/sec: 9.67

NODE 2:

Writes using 8KB random IOs - IOs/sec: 1149.83 MBs/sec: 8.98

Reads using 8KB random IOs - IOs/sec: 1645.81 MBs/sec: 12.85

Writes using 64KB sequential IOs - IOs/sec: 2319.13 MBs/sec: 144.94

Reads using 64KB sequential IOs - IOs/sec: 2081.33 MBs/sec: 130.08

I have now caved in and logged a Support Call with Microsoft as I think I have exhausted all my ideas!