As you move the slider you will get an explanation of what will trigger a migration at each of the levels. Pretty much this setting is just deciding how sensitive you want the DRS alogrithm to be for balancing the resources in the cluster.
Trust this helps.
Is it the below settings that you're wondering about?
Manual: vCenter will suggest migration recommendations for virtual machines.
Partially Automated: Virtual machines will be automatically placed onto hosts at power on and vCenter will suggest migration recommendations for virtual machines.
Fully Automated: Virtual machines will be automatically placed onto hosts at power on, and will be automatically migrated from one host to another to optimize resource usage.
Apart from level 1 which will only suggest or migrate a VM if there is a need to satisfy an affinity rule or a host is going into maintenance mode, the other levels are pretty much how tolerance you want in your cluster being unbalanced.
If you read through this link you can see that each migration suggestion is given a priority weighing and if this is less that what you set the slider to then a recommendation will be made to move the VM in order to bring balance back to the cluster
But this article says how to calculate which recommendations drs cluster will apply but what is the meaning of level 1,2,3,4,5 recommendations that i am looking for?
Ranjna Aggarwal wrote:
What is meaning of different levels in Migration Threshold in DRS?
In a very general sense it means how aggressive DRS will be to move VM around with vMotion. In setting 1 it will almost never do it, unless a Maintance mode or similar forces it, and the setting 5 will move VMs even if there is only a small chance of performance improvements. This might lead to too many vMotions going on when not really necessary.
For the actual priority value there is a quite complicated formula, but I am not sure if it is useful to study:
I've been looking for the meaning or causation of priority 1-5 recomendations as well. Did you find an answer? What would be taking place in the cluster balance or hosts that causes each priority recomendation?
Priority 1 - Affinity rules or Maintenance Mode
Priority 2 - ??
Priority 3 - ???
Priority 4 - ????
Priority 5 - ?????