Adding a Host to an HA VMWare Cluster

When adding a new piece of iron to a high-availability (HA) cluster your CPU compatibility matters.  HA means vMotion is involved and vMotion is able to bridge the various pieces of hardware using “Enhanced vMotion Compatibility” or EVC for short.  EVC is a mode you set that allows the servers to function at their highest common denominator, or rather, the greatest level of shared compatibility.  So, if you have a new system with all kinds of additional CPU capabilities but your old system is still L4 “Sandy Bridge” then your system must be setup to use L4.

  • L0 – Intel “Meron” Xeon Core 2
  • L1 – Intel “Penryn” Xeon 45nm Core 2
  • L2 – Intel “Nehalem” Xeon Core i7
  • L3 – Intel “Westmere” Xeon 32 nm Core i7
  • L4 – Intel “Sandy Bridge”
  • L5 – Intel “Ivy Bridge”

So… just use VMWare’s Compatibility Guide? No, you need to apply some common sense as well.  I just went shopping for an r720 to work with our ‘Sandy-Bridge” hexcore r710′s and found that the compatibility guides doesn’t really cover new systems very well.  Take a look at Wikipedia and look up your processor.  In my case, I have a choice of quite a few Xeon E5-26xx processors, but there is a note that the Xeon E5-2603 and Xeon E5-2609 do not have Hyper-threading capabilities.  Well, my other systems certainly do.  Also, these are quadcore rather than hexcore.  So, problem avoided.  I need to spend a couple hundred more on a proper processor so I don’t have to degrade my EVC Mode.


About Jay Farschman - Jay currently works as a Senior Systems Administrator for an asset management company in Colorado where he works with companies that produce hardware, telecommunications software and financial services.  Jay previously owned a consulting company and provided training and consulting services for three Fortune 500 companies and numerous small businesses where he leveraged Linux to provided exceptional value.

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