Transparent Page Sharing ignored in oversized VMs report?

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Transparent Page Sharing ignored in oversized VMs report?

Veeam Logoby dk2k » Mon Oct 27, 2014 9:03 am

Hey there,

as a big Fan of veeam B&R I am checking now veeam ONE - and already've run into an issue.
Veeam ONE recommends to size the Ram to peakvalue+30% and seems to ignore the Shared Memory completley!

Image

Considering VMware will disalbe TPS by default in future releases - wouldn't it be sweet if you had a "How much additional RAM do my hosts need if I disable TPS" report and to consider that value also in the oversized vms report?!?

So whats up with that? Hope you can help!
dk2k
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Re: Transparent Page Sharing ignored in oversized VMs report

Veeam Logoby Shestakov » Mon Oct 27, 2014 11:30 am

Hi Daniel,
Your feedback is interesting, could you clarify your use case?
So, you are using TPS for your hosts, planning to disable it and want to know what consequences it will cause. Is that correct?
Thanks.
Shestakov
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Re: Transparent Page Sharing ignored in oversized VMs report

Veeam Logoby dk2k » Mon Oct 27, 2014 3:15 pm

Yes, VMware will disable TPS by default @vSphere 5.1/5.5 from Q4 so that is a valid scenario for the future!
http://blogs.vmware.com/apps/2014/10/di ... tions.html

Windows VMs running Windows 2008 and higher can hardly use TPS because the OS encryts the RAM content, so vSphere can't deduplicate the RAM content.
But we run VMs that have many similar (unecrypted) RAM pages, therefore rely heavily on TPS, but still wanted to see if we could optimize our VMs.

For our example - As you can see our VM is sized at 10GB Ram.
The vSphere overview shows us, that ~0,9GB is activly used (orange curve) / 1,7GB max. and ~3GB are shared with over VMs (purple curve).

So without TPS the VM would be using 1,7GB + 3GB = 4,7 GB Ram (active) I suppose.

But the standard veeam ONE report (igonring the shared RAM) would rather tell me to size the VM to 2,4GB Ram (= 1,7GB + 30%) - and that would be way too low, because the VM would have to be set to 4,7 GB at the very least (so that the OS can see the 4,7 GB, regardless if the hypervisor can share 3GB with other VMs through TPS).

So yes you should make a new report "Disabling TPS Host Memory Requirements" and modify the default report that the recommended RAM size = active memory + shared memory ! Without that, the "oversized VM" reports / recommendations seem too dangerous to me.
dk2k
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Re: Transparent Page Sharing ignored in oversized VMs report

Veeam Logoby Shestakov » Tue Oct 28, 2014 3:43 pm

Daniel,

That`s interesting, previously VMware mentioned enabling TPS as a best practice and it seemed to be secured.

For provided VMs, what are your memory consumed results?

Thanks for the feedback, we will review our "Oversized VMs" report and think how to give an information about active/shared memory for the best resource allocation.
Shestakov
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