Speaking from experinece for AIX, I have done what you are asking about.
I went from dedicated AIX LPARS to virtual AIX LPARS that can be vmotioned on the fly running live without missing a beat or shutting anything down.
It is literally like magic.
We even pushed our luck to see how robust the vmotion was and even vmotioned in the middle of a HACMP fail-over and it survied that test.
This does give the system admins a nice way to clear all running servers off a physical box with no impact and then do system admin patches and reboots.
The thing to watch out for under AIX is the license is tied to the a physical box so in my case I need a license for each physical box I might vmotion my virtual LPAR to.
I have heard that other Operating Systems might have different licensing behavior like being tied to the MAC address, but I can defintely say AIX is tied to the physical box.
So that means one license will support as many LAPRs as a physical AIX box can handle.
The license file can also have multiple entries for the same cloverleaf object, so when it fails-over or vmotions to other physical boxes the single license file on our SAN that gets moved around will allow Cloverleaf to work for several different physical boxes.
You can even vmotions to an unlicensed box and cloverleaf will still run but if you stop anything it will not start.
So in an extreme case you could vmotion to an unlicensed box for a short time then jump back once emergency is resolved.
In my case I have 4 physical boxes but only 3 licneses so I have to put montoring in place to make sure I never get vmotioned for long to an unlicensed physical box.
Also, I put montioring in place to check that both my active and passive HA nodes aren’t unintentionally running on the same physical box, which essentially makes the HA null when that stupid mistakes occurs.
This has been the licensing behavior for AIX on every version of Cloverleaf from 3.5 – 6.0 that I have installed.
There is also a useful command within cloverleaf called hcilictest that will confirm if a given license entry is okay on a given box.
So once you think your licenses are correct, vmotion or fail-over from box to box to see which ones are report okay by running hcilictest before making assumptions that could bite you later on.
Russ Ross
RussRoss318@gmail.com