Memory Oversubscription on ESXi 4.1

[karapakr]

Hello,

Thought i`ll seek the opinion of the community before going ahead with proposal:

VSphere 4, ESXi 4.1, 3 hosts N+1 cluster, HA and DRS enabled:

• Total memory - 192 GB
• Usable Memory - 128 GB (on n+1  basis)
• Allocated/Consumed memory for all 46 VMs  running on this cluster - 165 GB (85% of total available)
• Total Avg memory consumption/Active Memory  used/VM Memory Demand on entire cluster =~ 25 GB
• No memory reservations on existing VM and no limits as well

Ofocurse quite apparant that memory is over allocated for the exisitng VMs. Re-ALlocaiton to be done in second phase.

Since the active memory is just 25 GB, deploying 12 more VMs with total of 48 GB memory requirement is a good idea or not?

Will the cluster allow me to deploy these new VMs at all as the remaining unallocated memory is just 27 GB?

In general, can allocate ,more memory than the available physical memory?

Response and ideas are very much appreciate.

[marcelo_soares]

If you have ha and it have the admission control enabled, you may not be able to power on these new vms. On the cluster summary tab, you will be able to check how many more memory you can use.

Memory overcommitment is a common practice, you can use it with no problem. Just keep an eye on ballooning and swapping, when you start to have them you will need to rethink your memory distribution.

[karapakr]

Marcelo,

Thanks a lot. I`ll check on this point. Admission control would be the key.