How many VMs we can deploy from template concurrently?
I have never tried to see how many can be deployed off a template at once. We typically do a couple at a time. If you have a VAAI capable array to offload some of the I/O, you should be ok.
I don't see a maximum listed in the http://www.vmware.com/pdf/vsphere5/r51/vsphere-51-configuration-maximums.pdf
8 per host ...
Concurrent Operations
Concurrent vMotion operations per datastore 128
Concurrent Storage vMotion operations per datastore 8
Concurrent Storage vMotion operations per host 2
Concurrent non‐vMotion provisioning operations per host 8
I use the below method and normally don't do more than 2 at a time. I have seen weird issues with doing more than 8 at a time.
http://www.knightusn.com/home/vmdeploymentwithpowercliandcsv
-vFantastic