ESXi

Hi ,

I have a question regarding memory sharing in ESX. Can the memory blocks be shared between different types of OS (NT4,W2k,W2003,W2008) as long as the memory blocks "matches" ? Or is the memory block "tagged" with "W2003 only" ?

There is a counter you can look in performance called memory shared ,you find it under memory. Is that the number of shared memory between vm´s in the ESX host ?

regards Stefan

Hi,

I'm not sure but I think that TPS looks for sharing RAM between the same type of guest OS.

This is determined by the options you've defined in your VM (not really the guest OS). Also you may know that this is also related with CPU/MMU virtualization: using software MMU virtualization doesn't share RAM.

There is a easy place to see if you are sharing memory is in the Summary tab of any of your Resource Pools.

Regards .

Hi,

Check this link and search for Memory Sharing above Memory Overcommitment.

(it's for ESX 1.5, but I think the action should be the same, because as long as theres a share memory, VMs use it but as soon as they want to change, they will use their own memory)

It seems that the feature uses for same OSs and also matches block. just like you said, same block from windows 2003 vms, share same mem (for example, tag=share1), same block from Windows 2008 VMs, share same mem (for example, tag=share 2).

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MCTS, VCP

http://www.kasraeian.com

It does not matter wht OS has stored the page - as long as the page is the same it is shared in Read only Memort and the when the VM goes to write to the page a copy is made and the write is made -

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Hi,

Thanks for your help, I would be grateful If you cloud guide me about, where can I find document or information about it or what should I search, because I search and the result was that link I had send in my previous post in this thread.

Again thanks

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MCTS, VCP

http://www.kasraeian.com

You should read this thech paper from VMWare. http://www.vmware.com/files/pdf/perf-vsphere-memory_management.pdf

Regards.

I'll start reading it tonight. :smileywink:

Thanks in advance.

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ESX doesn't care about "Windows 2003" or "RedHat 4". If two blocks are absolutely the same - one be eliminated and replaced with link.

There are two counters - Memory Shared and Memory Shared Common.

Common - is a sum of all unique blocks that are shared. And Shared is a sum of all blocks shared, so real memory Economy = Shared - Common.

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MCSA, MCTS, VCP, VMware vExpert '2009

http://blog.vadmin.ru