Choosing the reserved cluster failover capacity

By now, we all know that VMware has introduced a Percentage-based cluster resource reservation model. Using this setting, you need to specify how much resource you want to reserve for accommodating host failure. It also allows us to select different percentages for CPU and Memory.

You might wonder how would you calculate how much resource you want to reserve for your HA cluster. While it was a straight-forward approach when we used to select number of hosts reserve for servicing a host failure, we have seen disadvantages as well. If you use the number of ESXi hosts failure in your HA cluster, you will reserve those completely, thus it will not be efficient to tune in your HA cluster or put it into best use. Also it avoids the commonly experienced slot size issue, where values are skewed due to a large reservation.

Percentage-based reservation is also much more effective as it considers actual reservation per virtual machine to calculate available...