Very informatory link as per your query.
that depends on many factors
do you use thin provisioned VMs ?
do you use snapshots ?
do you run automatic backup-tools ?
the formula I use for LUNs that use thick provision and no snapshots is
for every VM that usually runs on that LUN sum up its vRAM + 1 Gb
so if you have 10 VMs using 4 GB of vRAM the result would 50 Gb as the minimum required free space - enough to suspend each of them in an emergency.
If you use snapshots or thin provisioned VMs you of course need more than that
Thanks for your reply.
We don't use Thin Provisioned LUNS
We use Snapshots & our backup solution is Netbackup that uses Snapshots.
How do I work out how much free space is needed in this case?
the idea is to survive at least one day ...
so assume your backup-tool runs amok and does not clean up the daily snapshots
do a rough calculation of the space required for such a scenario and add that to the value you need for a emergency suspend of all VMs