A: My last Q&A gave you the calculation DRS uses in prioritizing its migration recommendations. But while priority 2 through 5 recommendations are all based on their impact to resource entitlements, priority 1 recommendations are a special case.

Priority 1 recommendations are considered mandatory, because they must be completed in order to preserve the requirements of a policy or rule. Examples of these required migrations include hosts that enter maintenance mode or standby mode, a violation of affinity/anti-affinity rules, or when VM reservations on a host exceed that host’s capacity. With the exception of putting hosts in maintenance or standby mode, these situations happen relatively rarely. So, you won’t often see many priority 1 recommendations in your cluster’s DRS tab.