#1 I am assuming that I need to create a lun that will be mapped by all of my ESX servers that I intend to use vmotion. Is this assumption correct?
Correct the vmware datastore needs to be visible to each ESX host that will participate in Vmotion
#2. Should I create on gianormous lun and put all of my VMs in that lun or should I create multiple LUNS and make point all ESX servers to each LUN for vmotion purposes
The general best practice from most SAN vendors is no more than 10 virtual machines in a single datastore,
Having said that, like most best practices, this is a conservative setting that may not be the best for your specific environment.
The limit of 10 machines is related to the relatively high cost of writing new metadata into the VMFS filesystem and the performance impact this may have. Because this filesystem will be shared by miltiple servers, updating the metadata requires a SCSI reserve and release. Vmware's efficiency in using these scsi reserve and release requests has improved in the latest versions of ESX, however it still pays to be cautious.
The things that cause metadata updates include
1. Starting and stopping a VM
2. Vmotioning a VM
3. Using Vmware snapshots
4. Using VCB (Vmware consolidated backups - as these use vmware snapshots)
If you dont think you'll be doing much if any of these kinds of operations, then having more than 10 virtual machines per VMFS datastore/LUN may be OK, if on the other hand you think you'll be using lots of Vmware snapshots with lots of write I/O, then 10 may be too many.
If you use NFS, these issues no longer apply as the WAFL handles metadata updates without needing SCSI reserve/release mechanisms. As a result you can safely put a lot more VMs into a datastore without having to worry about performance, this is particularly useful in VDI deployments.
The trouble with lots of smaller LUNs is that you have the potential to lose a lot of space in the unused portions of your VMFS datastores. This can be mitigated through the use of thin provisioning of the LUNs, which works beautifully and elegantly, however it also requires that you set up the appropriate monitoring/alerting mechanisms to ensure that you dont run into any problems.
If you're new to NetApp, or are unfamiliar with thin provisioning, it would be wise to take the time to learn how this works before rushing into things.
Regards
John