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logiccomm
Contributor
Contributor

100% memory reservation

Hi all,

In our environments we do not overcommit memory; if a host has 256gb of RAM, then the combination of guests will not exceed 256gb.

Forever we have left the memory reservation at 0% which means that on boot, a swap file of equal proportion is created... and it's never used.

Are there any limitations, gotchas or comments that anyone can make about limiting all VMs to 100% memory reservation? This will reduce our storage consumption by a considerable amount across the board as the swap file will be reduced to 0 bytes.

Thoughts?

Thanks.

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brunofernandez1

just one question. why do you not overcommit the memory? this one of THE reason to virtualize system Smiley Happy

features like, balooning and page sharing are no more possible with that Smiley Sad

if you wanna reservate the VM ram, take care to leave a rest for the esxi operating system/vmkernel

but i would not recommend in your case to work with reservations

------------------------------------------------------------------------------- If you found this or any other answer helpful, please consider to award points. (use Correct or Helpful buttons) Regards from Switzerland, B. Fernandez http://vpxa.info/
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logiccomm
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Hi Bruno,

My understanding around overcommitting RAM is that any changes will get swapped to disk, and thus there's a greater reliance for having fast and low latency disk available for this. Physical memory is not so much of a problem in our environment.

Thanks.

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brunofernandez1

take some time and read thsi document:

http://www.vmware.com/files/pdf/perf-vsphere-memory_management.pdf

this will help you understanding how memory is managed

as I said I would not recommend to work with reservations for ALL VMs.

if you need more diskpace i would try to go ahead with thin provisioned disks and so on...

------------------------------------------------------------------------------- If you found this or any other answer helpful, please consider to award points. (use Correct or Helpful buttons) Regards from Switzerland, B. Fernandez http://vpxa.info/
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