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Danstr1
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VMWare VSPhere 5 HA and Available Memory

I'm relatively new to VMWare and have a question that relates to HA.  I have HA installed and configured which has been tested and working properly this far. My environment is fairly straight forward with two hosts that share storage (VSphere 5). For sake of ease, let's say that I have 4 VM's working on each of my host machines. Each of these servers has 6 GB of RAM assigned to it so the actively used RAM is 24 GB. Each of the host machines has 48 GB of RAM so there is always 24 GB of free or available RAM if HA should need to use it. I need to add a 9th VM to the mix. So now one of my hosts (host A)  has 30 GB of RAM assigned and 18 available. If either Host A or Host B were to go down, there now isn't sufficient RAM. So my question is, if there are 5 machines with 6 GB of RAM assigned each, does HA require the full 30 GB or does it take into consideration the amount of RAM the VM's are actively using. Say that each server was actively using no more than 4 GB of the allotted 6. Will HA then require only 20 GB or does it require the full 30 GB as assigned to the VM's?
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Danstr1

8/22/2022 - Mon
ASKER CERTIFIED SOLUTION
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

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Danstr1

ASKER
As an additional note, the Admission Control policy is set to "Disable: Allow VM power on operations that violate availability constraints." Is this my answer? As long as I retain this setting then I can assume (within reason of course) that my servers will all restart via HA on the opposing server? I do have the priorities set appropriately so the less critical servers will be starting last when the performance might lag due to inadequate resources.
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

Yes, correct if you have that option set, VMware HA will failover and work.
Danstr1

ASKER
Our postings crossed! Thanks for the quick and detailed answer. Very helpful!
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Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

No problems.
Danstr1

ASKER
Very detailed and helpful. Thanks!