For those of you considering the vSphere Storage Appliance as a shared storage solution, I bring you a piece of very good news. The RAID10 configuration requirement on the hosts has now been relaxed. As of today, VMware will now support RAID5 & RAID6 configurations alongside the original RAID10 configuration. This will mean that even more local storage can now be utilized as shared storage (NFS datastores). This is a common feature request that we heard from a lot of potential VSA customers, so I'm glad we've been able to pull this into VSA 1.0.
The VSA documentation already reflects this change in support.
vSphere Storage Appliance Planning Checklist
The VSA cluster requires RAID volumes created from the physical disks. VMware recommends that you use RAID5, RAID6, or RAID10. The vSphere Storage Appliance uses RAID1 to maintain the VSA datastores’ replicas. The capacity of the VSA datastores depends on the number of physical hard disks and the RAID configuration that you use. The actual realized capacities are calculated separately for RAID5, RAID6 and RAID10.
--> Please see the rest on the blog : http://blogs.vmware.com/vsphere/2012/01/raid10-requirement-for-vsphere-storage-appliance-vsa-relaxed.html