VMware Swap- Rules of Thumb with NetApp?

We frequently get questions from customers with NetApp if they should store the swap with the VM or on a separate datastore, and how big should they make their swap datastore.

NetApp recommends in NetApp TR-3749 to use a separate datastore, as to avoid storing “transient” data like swap when using array based snapshots or disk-to-disk replication with SnapMirror and/or SnapVault. (Also See TR-3428).

For sizing, you can thin provision and use autogrow on the NetApp side to avoid having to worry about an “exact” space figure as this space is dynamic in nature depending on the number of VM’s, the memory in those VM’s, and memory reservations, and is used only when there is memory pressure.

If you want an absolute worse case add up all the VM’s you would create with the memory you anticipate allocating to them, and use that result if you need an absolute worse case number.