On Fri, 7 Sep 2012, Ray Van Dolson wrote:
VMware has Fault Tolerance ("FT") which essentially keeps a mirror VM
running on another host. Literally a mirror. If you open the console
of them both simultaneously you'll see your mouse cursor move on both
at the same time. :)
This lets you survive a host outage in any case with some drawbacks.
Theproblem is that the physics of the problem make this not actually true.
There is going to be some lag betwen updates happening on one system and
them being replicated to the other system.
To the naked eye, they are not going to be visible.
To testing, especially under low load levels they may not show up
but under high (i.e. production) loads, and when hardware starts to fail
and so doesn't quite behave the same way it does normally, you are far
more likely to run into a problem.
Depending on your situation, this may be acceptable, or it may not.
It sure is a nice idea to not have to think about HA because the
virtualization handles it for you, but you need to not drink the kool-aid
and believe that this can guarantee seamless failover.
David Lang
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