Hi John,
The main issue was, currently our 5 hosts have 7200RPM sata disks with intel SSDs. We have only had 2 SSD fail the whole time so not too stressed about the fact they are failing, its more the struggle the system has resyncing. Murphys law it happens early in the morning just before the peak load when everyone is logging into the vms, the resyncing is still happening and the vms is extremely slow, to almost unusable. We have 10G to each host but it is on 3750 Cisco switches so I know the latency isn't brilliant and we are looking at infiniband for our next cluster build and will go PCIe for flash and all SSD for storage, but that's a ways off yet.
So my original query with adding a second flash SSD into the disk group is purely to avoid the disk group going offline and the system needing to resync causing these times of heavy lot. I know the Sata 7200 disks aren't great but I wouldn't have expected its a heavy io load process resyncing, more sequential reading and writing of data, so wasn't convinced the Sata disks were solely responsible for the bottleneck when resyncing.
So if adding a second flash SSD to each disk group isn't really an option to keeping them online in the event of an SSD flash disk failing then looking at the additional striping and setting FTT to 2 as a means of keeping the system more stable and usable when this happens??
Cheers