The limit is 256 which you can mount to ESXi 5.0/5.1/5.5: Set NFS.MaxVolumes . But its all depend upon the performance of the particaly machine under the workload . While designing the CPU and Storage workload we always suggest the CPU should not be load more than 80% in any case. In the same way the storage we decide it should always depend on the Type of workload sequential and random .
So all in all i would suggest the no of NFS datastore upto the machine is working fine .
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