Several months ago, I ended up in an unfortunate situation. We invested a sizeable amount of money on a powerhouse server to add to our ESX cluster. While the server was the same model as the rest of the machines in our cluster, the vendor had added SSSE3 support to this latest revision, something I was not aware of at the time of purchase. The end result of adding these new instructions to the cluster was vMotion incompatibility between this server and our other ESX hosts.
While not supported by VMWare, CPU masking is a feature available in Virtual Center that will allow you to overcome situations like this. While in my case, SSE3 servers to an SSSE3 server, compatibility certainly cannot be guaranteed in these situations and I must emphasize that you proceed with caution. In addition, if the differences in my CPU's were more profound (say AMD vs. Intel), I would never attempt this, especially in a production environment.
In some situations, Enhanced vMotion will allow you to overcome minor CPU differences and I would certainly recommend that as a first attempt. You will need to be running at least Virtual Center 2.5 Update 2 and ESX 3.5 Update 2 to enable this. You will also need to recreate your cluster. You can find information on EVC as well as supported processors in KB 1003212.
VMWare outlines the process of CPU masking in KB 1993. In my case, I wanted to mask only the needed instruction sets and it took a little while to figure out exactly which combination of masks to use between each of the registers leveraged. The end result was to navigate to C:\Documents and Settings\All Users\Application Data\VMware\VMware VirtualCenter and edit the vpxd.cfg XML configuration file. The section of text below was all that was needed to accomodate the differences between these processors. Sorry for the screenshot, but formatting XML for web presentation is a pain...
While not supported by VMWare, CPU masking is a feature available in Virtual Center that will allow you to overcome situations like this. While in my case, SSE3 servers to an SSSE3 server, compatibility certainly cannot be guaranteed in these situations and I must emphasize that you proceed with caution. In addition, if the differences in my CPU's were more profound (say AMD vs. Intel), I would never attempt this, especially in a production environment.
In some situations, Enhanced vMotion will allow you to overcome minor CPU differences and I would certainly recommend that as a first attempt. You will need to be running at least Virtual Center 2.5 Update 2 and ESX 3.5 Update 2 to enable this. You will also need to recreate your cluster. You can find information on EVC as well as supported processors in KB 1003212.
VMWare outlines the process of CPU masking in KB 1993. In my case, I wanted to mask only the needed instruction sets and it took a little while to figure out exactly which combination of masks to use between each of the registers leveraged. The end result was to navigate to C:\Documents and Settings\All Users\Application Data\VMware\VMware VirtualCenter and edit the vpxd.cfg XML configuration file. The section of text below was all that was needed to accomodate the differences between these processors. Sorry for the screenshot, but formatting XML for web presentation is a pain...
No comments:
Post a Comment