Hello MrVmware9423,
It would be better to go ahead with two Lun's of 2TB each. Saying that, it always depends. Single big lun and smaller lun both has its positives and negatives.
A single bug lun would be easier to manage, but it will host more number of VM's. In that case locking would be more. it is always suggested to have somewhere around 15 - 20 VMs per LUN (server grade). Again it varies depending on the VM size and stuff. Also when you have a single lun of big size the IOPS would also be limited to the backing disks only related to those LUNs.
Whereas more smaller luns would be complex to manage, but would result in lesser lock and IOPS would be distributed over LUN's.
For further reading you can check these:
http://www.vmware.com/pdf/Perf_Best_Practices_vSphere5.5.pdf
Also check the following:
You might want fewer, larger LUNs for the following reasons:
■ | More flexibility to create virtual machines without asking the storage administrator for more space. |
■ | More flexibility for resizing virtual disks, doing snapshots, and so on. |
■ |
You might want more, smaller LUNs for the following reasons:
Saying the above 2TB Lun size with 15 to 20 VM per datastore seems to be sweet spot for most of the cases