This is usually a really fun late night affair :-)
Here are the basic steps outlined for an easy pain free move:
1. Pause passive node in Cluster Administrator then take passive cluster node offline
2. Add new HBA's
3. Fire up passive node, connect fibre from HBA's to fibre switches on new SAN and configure zoning etc.
4. Present disks to passive node, then re-scan via disk managenet and ensure you've picked up new disks
5. Add drive letters and format
6. Fail cluster over
7. Take cluster offline, add disks as Physical Disk resource in Exchange Resource Group and add disks as a dependancy of SA.
8. Bring cluster online
9. On new passive node repeat steps 1 through to 4.
10. Fail cluster over to ensure both nodes can successfully bring their resources online and see both disks
11. Now just move the databases via ESM to new SAN disks.
12. Quorum is moved in Cluster Administrator
13. EVS disk - I take the cluster offline then copy all EVS data to the new EVS disk.
14. Once that is done remove the EVS disk from Cluster Admin and add the new EVS disk with the original drive letter name. Then bring cluster online.
15. Removing the old SAN hardware - removing the disks from Cluster Admin and then at an appropritate time take each node down and remove legacy HBA's
16. Power down legacy SAN and remove from racking
MVP - Exchange Server