Today I dove a little bit more into DRS, or Distributed Resource Scheduler. DRS is an incredibly useful functionality in vCenter, it allows VMs to be moved, or give suggestions on how they should be moved, based on resource utilization and when hosts are brought down for maintenance. There’s manual, partially automated, and automated DRS. With manual you simply get recommendations on how to move VMs, with partially automated the VM is automatically placed onto a host based on DRS and then if the VM should be moved DRS will actually give recommendation, and automatic, my favorite, allows the VMs to be vMotioned automatically based on host being in maintenance mode and resource usage. Of course there are prerequisites. You must have a gigabit port on each host in the cluster you are enabling DRS on and have vMotion assigned to that vmKernel(VMK), other services can run on this VMK with vMotion, vMotion is what is used to actually migrate the VMs DRS is only performing calculations and determining where and when they should be moved. There are multiple other features that you can enable that work alongside DRS as well once enabled which include predictive DRS which allows DRS to make predictions with help from vRealize and move VMs before problems occur. There is also DPM, Distributed Power Management, which has the ability to power on or power off hosts based on resource utilization. Power definitely isn’t cheap for those big datacenters so this is a useful one to possibly turn on. DPM also has manual, partially automated, and fully automated similar to DRS. Then finally there’s EVC, Enhanced vCenter Compatibility, to better understand this feature I should note that if CPU architecture is different, say one host is using an older intel processor then another, it is likely vMotion will fail. In this case you could enable EVC and set the minimum baseline for the cluster, or the VM, to the older CPU on your cluster and EVC would hide those newer generated CPU instructions and simply run all hosts at that baseline architecture allowing live vMotion migration between different CPU architectures. THIS DOES NOT WORK WITH DIFFERENT VENDORS. EVC will not allow you to vMotion VMs running on intel processors to AMD. However if you do a cold migration by powering off the VM first cross CPU vendor migration is possible. This has been my longest post yet, but I have to say there was a lot to talk about and I ended up having to summarize quite a bit.