Storage provisioning question

[twns]

I have two hosts with local storage that I'm attempting to provision via CMC > new cluster and the cluster information in the CMC shows  cluster available size size as 693GB, which looks correct but if I choose the thick provision option it will only allow me to provision 347GB. If I choose the thin option it accepts and I can move on but I'm concerned with overprovisioning.

Each of the hosts has 350GB available to allocate. Is this due to the RAID 10 "mirroring option"?

[a_o]

Yes.

Given that you have 2 nodes, with NR10 Luns, your provisionable (thin or thik) storage in a cluster would be half of your total available storage.

With NR5 (3 or more nodes) , NR50 etc, your provisionable storage would be 33% of available storage or less. 

With thin provisioning, it's possible to over-provision.  However, as you get closer to comsuming the your total available storage, you would just add more storage by scaling out or scaling up.
It's easy to scale up with VSAs, as you can just add more underlying storage and present them to the VSA. You can also increase VSA capacity by addinng more nodes to the cluster  (scale out).  With the physical appliances, you can only scale out, your only option is to add more nodes to a cluster.

[a_o]

Just one more thing...

Is this due to the RAID 10 "mirroring option"?.

IMO, there's no point to using Storevirtual if you're not doing some form of Network RAID.

The main feature of StoreVirtual is the protection offered by Network RAID. In essence, you'll have two or more copies of your data on the SAN.  Yau can lose one or more nodes in a cluster and your data would still be avaialble to the initiator hosts. Having two or more copies means that your data takes at least twice or more raw space that's available  on the SAN.

i.e. In NR10, a 50GB LUN takes 100GB on the SAN - each node having 50GB of it's available space consumed by that LUN.