With the option to provision a thin disk using vSphere or at the SAN layer, which option is best? Is it feasible to provision at both the SAN and VMDK levels or could that end up causing confusion. I imagine that SAN thin provisioning would offer better performance too?
I would always thin provision at the storage layer if possible as the additional load, although small, is placed on the SAN storage processor or array controllers rather than the ESX hosts when handle block allocations.
I think either way will work, the important part is how we manage here and you may need to consider the I/O loads on each datastore. Too many virtual machine or virtual disk on same datastore will impact to the performance too. At the same time, you may not want to over provision too much as datastore full will cause virtual machine to be freeze or unrespond.
Also just to add something from personal experience in regards to TP... Make sure you align your disks properly, as it plays even more of a role in TP disks vs. thick. Regardless of where the thin resides, if you start growing mis-aligned disks you are going to watch what should be a 1 or 2 IOP into 2 or 4 IOPS... It doesn't matter where it happens, that's bad news for IO
Thomas H. Bryant III
Director, Advanced Technology & Products
VMware Communities User Moderator