Fault Tolerant capable CPUs that are not Fault Tolerant compatible
Administration, Tips and Tricks Add commentsToday I ran into this issue with a customer and wanted to write on it so it does not happen to everyone. Fault Tolerance on vSphere is an awesome solution to maximize uptime. There is a CPU scenario that may be a challenge however:
This KB article (http://kb.vmware.com/kb/1008027) reads:
For VMware FT to be supported, the servers that host the virtual machines must each use a supported processor from the same category as documented below:
Intel Xeon based on 45nm Core 2 Microarchitecture Category:
3100 Series
3300 Series
5200 Series (DP)
5400 Series
7400 Series
Intel Xeon based on Core i7 Microarchitecture Category:
3500 Series
5500 Series
AMD 3rd Generation Opteron Category:
1300 and 1400 Series
2300 and 2400 Series (DP)
8300 and 8400 Series (MP)
Please note the requirement “same category.” As an example, if you have a server with a 54xx series Intel Processor and a Intel 55xx series processor (both have the technology for FT), you can vMotion and DRS between them (via EVC) but you cannot run a Fault Tolerant pair across them. The Lockstep technology from Intel changed in the 35xx and 55xx CPUs and is not compatible with the previous generations of lockstep.
November 10th, 2009 at 2:43 pm
Interesting, does the Check Compliance function highlight that ?
November 10th, 2009 at 6:44 pm
Hi Dave,
I appreciate the great information you provide on this blog, top notch stuff.
We implemented VMWare’s vSphere 4 a few months back and heard this limitation repeated by both VMWare’s folks and the reseller we had engaged to help us. I don’t believe the vSphere client will even let you enable FT if the two hosts aren’t compatible will it?
Also what about running FT within a nested VMWare vSphere 4 cluster, a VM environment within a VM environment? I didn’t actually realize until recently you could run nested VM environments at all.
Cheers!
November 10th, 2009 at 8:45 pm
Yes, vCenter will check to make sure that FT will work before you enable it. You can also use the site survey tool to find out if you can use FT on your hardware before you install it (http://www.vmware.com/download/shared_utilities.html).
You cannot run FT when running ESX nested (Esx running inside a VM).
November 10th, 2009 at 9:56 pm
Just wanted to add that less expensive AMD Athlon X2 Kuma model CPUs and AMD X4 Phenom 9650 CPUs will do VMware FT with Opteron Quad 1352, 1354, 1356 CPUs (or between themselves), although not in a supported configuration since only the Opteron CPUs are supported.
Also, expanding upon what was said above about VMware FT not working with nested ESX hosts, it may appear that VMware FT works initially but after a short while the syncing efforts between the Primary and the Secondary VMs can’t keep up and eventually communication with the Secondary VM will stop.
Datto
November 17th, 2009 at 9:32 am
It’s interesting that, after going through the bother of matching processors on multiple servers, VMware FT can make use of only one core per processor. VMware FT is not SMP compatible.
November 18th, 2009 at 9:41 pm
Correct, currently you can not do SMP VM’s as Fault Tolerant pairs. However, having said that, I don’t believe any other hypervisors can do Fault Tolerance at all if I’m not mistaken. (Sorry if I sound a little arrogant there, it’s just really cool technology that no one else does).
-Dave