VMware EVC cluster, what is that?
I have had several customers asking me for advice on what to do with new ESX hosts who should be joined into the VMware cluster, but after adding to the cluster problems with vMotion arose. It just didn’t work anymore because of some minor CPU differences.
One of the customers had bought the exact same HP DL380 model with same product number and revision with the same type of Intel CPUs inside. But unfortunately the stepping on the old CPUs is 6 and on the new ones its 10. The HP machines contain Xeon CPUs from Intel type 5450 3 Ghz stepping 6 (existing) and stepping 10 (new).
I asked them the following questions so I could give them advice on what to do next:
Question: How many new ESX hosts are you adding to the cluster?
Impact: If you are just adding 1 or 2 ESX hosts as extra capacity it is good to look into reforming the VMware cluster to an EVC cluster., because the more ESX hosts (up to 32) in a DRS cluster the better DRS can do its job. If you have more than 2 hosts to add to the cluster it can be a solution to build a dedicated cluster with the new ESX hosts.
Question: Do you need the new features added to the CPUs or do you just need more power in the VMware cluster?
Impact: If you look at the latest range of CPUs it can make a total difference of up to 25% speed, because of new added features.
Question: What are the plans for the future with the clusters and do you suspect significant growth?
Impact: If you suspect significant growth it can be useful to build up a new ESX cluster with new functionality but always weigh carefully the pros and the cons.
Question: Are the used servers and CPU’s capable of switching on the VT or AMD-V option and can the XD or NX bit be enabled in the BIOS? (Intel markets the feature as the XD bit, for eXecute Disable. AMD uses the name Enhanced Virus Protection.)
Impact: If the machine and the CPUs are capable, you can start using an VMware EVC cluster.
After answering the above questions I recommended some clients to build up an EVC cluster in vCenter Server, most answers I get after suggesting such a move are:
“uhhh build an EVC cluster, what’s that?”
