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GiovanniC
Contributor
Contributor

vmotion and CPU compatibility just in one direction

Hello, I need to vmotion virtual machines

from:

ESXi 4.1 host (CPU Intel® "Nehalem" Generation) L2 EVC mode

to:

ESXi 5.5 host (Intel® "Sandy Bridge" Generation) L4 EVC Mode

but no need to move back (from L4 to L2), because the ESXi 4.1 will be retired after VMs will be moved out

reading the VMware KB: VMware KB: Enhanced vMotion Compatibility (EVC) processor support :

In general, if a processor can support EVC level XN, it can also support levels XN-1 to X0. For example, a processor that supports the Intel® "Sandy Bridge" Generation EVC Baseline has an EVC level of L4. Therefore, it can also support EVC levels L3, L2, L1, and L0.

.... I deduce that could not be necessary the EVC enabled at L2 on both cluster (ESXi 4.1 and 5.5) if I need only to move VMs from CPU Intel® "Nehalem" Generation host to Intel® "Sandy Bridge" Generation host, .... but I'm not sure and at the moment I cannot test it.

has someone tested it? any help or opinion is very appreciated.

Thanks in advance.

Giovanni


4 Replies
ClintColding
Enthusiast
Enthusiast

Both clusters will need to be running EVC mode L2.

Here is a good read on the subject: http://www.virtualizemydc.ca/2013/10/25/vmotion-virtual-machines-between-clusters-with-different-hos...

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LikeABrandit
Enthusiast
Enthusiast

Actually, if you're migrating from a lower EVC mode to a higher, you should be able to do so with powered on VMs since the features currently used by your VMs will not be masked on the destination and because allowing additional features that the VM won't access anyways won't affect it. It's the reverse that can't be done, because since the VMs are actively using features which will be masked when they arrive on the new host, they need to be powered off first.

You can easily confirm this without actually migrating by selecting a VM you want to migrate that is powered on, selecting Migrate, and choosing the host/cluster you want to migrate to. vSphere will perform a validation check and let you know whether you're in the clear or not.

Note: There is a caveat to migrating from lower to higher EVC modes. The VMs migrated this way will not use any of the additional features that are unmasked between L2 and L4 until they are powered off and then on. This does NOT include a guest level restart. The features for a given CPU are selected at power on, which does not occur on a soft reboot of the OS. You need to fully power off and power on the VM to allow those features to be utilized.

~Brandit

GiovanniC
Contributor
Contributor

Thank you for your answers,

so...  don't we need the EVC functionality enabled on both cluster to move virtual machines from a cluster with Intel® "Nehalem" Generation CPU's to a cluster with Intel® "Sandy Bridge" Generation CPU's, correct?

Giovanni


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ClintColding
Enthusiast
Enthusiast

Yes LikeABrandit is correct, you can vMotion in the one direction but EVC has to be enable on both clusters. I misread your OP.

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