VM Junkie

May 24, 2009

vSphere Tidbits Number 2

Filed under: Uncategorized, vmware, vSphere — ermac318 @ 6:16 pm

I’m chronicling some of the cool things I discover as I go along playing around with vSphere. This time, some stuff about Fault Tolerance!

First off, if your CPUs are not FT-compatible (check here) then it won’t even turn on. So unfortunately, it’s not one of those “it works but is unsupported” deals, unless there’s some way to turn off the CPU checking that still needs to be discovered. This has already bitten us in the lab…

Next, if they are compatible, then you need to turn HA on. So far it seems like HA is much more tempermental about DNS in 4.0 than it was in VI3.5 (even pre-Update 2). For example, do NOT add your hosts to vCenter by IP address if you want to get HA to work…

Also, FT is actually really flexible once you get it turned on. You can migrate not only the primary node but also the secondary. This can be important if you want to make sure your two FT nodes are in separate blade chassis, or even different datacenters if you’re doing stretched ESX clusters.

Finally, You can actually Open a Console to each VM (the secondary gives you a warning that it’s read only) and watch what you do on the primary VM get replayed in near-realtime on the secondary node.

I think FT is a really neat feature, and despite all the caveats (no vSMP, no thin provisioning, no snapshots, etc) I still think it’ll be a really great feature that can only get better!

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