DRS and Resource Allocation

[kuay5]

Hi all,

When should DRS be used and when should resource allocation. Because i have the impression that this 2 features contradicts one another. DRS allows VMs to use resources from other physical hosts right? And resource allocation sets how much a group should use right?

[john23]

This doc would be helpful for you

http://www.vmware.com/pdf/vi3_35/esx_3/r35u2/vi3_35_25_u2_resource_mgmt.pdf

-@m!t

[kesparlat]

Hello kuay5,

Not in all scenarios those 2 features are contradictory. If you want to assure a specificic performance for a VM you can set a reservation for this one. Additionaly you can have other resource pools and DRS.

Regards

[weinstein5 · Accepted solution]

Welcome to the forums - They are not contradictory at all - remember DRS is desigined to insure that the VMs get the CPU/Memory resources they need. It does this by monitoring the resource consumption on each host in the cluster and which host can provide those resources. Since a VM can only use the resources form a single host at a time, if a different host has more resources DRS will vmotion that VM to it-

Now if you set resource allocations to the VM DRS will use these to determine which host will best satisfy those constraints and demands - and when set resource allocations at a pool level you are carving out resources from the cluster - really this used to divide the resources in a DRS cluster up to different groups - the best example of this is splitting resources between test/dev and production so that the Test/Dev does not monopolize the resources depriving the production VMs -

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[kuay5]

Thanks alot guys. Your comments and links really helped clear my doubts.