Hi,
during a SMVI backup, we request from VCenter that a consistent vmware snapshot be taken from the VMs in the datastore. After VC/ESX takes a consistent vmware snapshot, we take a NetApp filer snapshot of the volume that hold the LUN or of the nfs volume. At the end, we requested from VC to remove/delete the vmware snapshots.
I guess your question is for the vmware snapshot. Yes, VC can take only a few amount of vmware snapshot at a time. I believe 6.
From SMVI 2.x or VSC 2.x, you can increase this number in the smvi.override file. But note that setting this number too high can have another impact in the ESX environment.