Memory overcommitment

Monitoring and reporting for Veeam Backup & Replication, VMware vSphere and Microsoft Hyper-V

Memory overcommitment

Veeam Logoby remko.de.koning » Wed Mar 18, 2015 1:05 pm

Hi guys,

We have an issue that we cannot explain. That is, we don't understand why.
We have three HP proliant servers in a Hyper-V cluster. Each host has 160 GB of memory. In total 3 X 160 = 480 GB
Just recently, after adding a new VM, we reached approx of 200 GB in use memory which triggered a "Cluster memory overcommitment" alarm.
After investigating on the issue we noticed in the Veeam graphs that Veeam think that approx 200 GB is equivalent too 100% memory
Left side of the graph shows amount of GB memory. Right side of the graph shows Memory in percentage.

Why is Veeam showing the 200 GB as 100%?

We have designed the cluster in such a way that one host can fail and that we can continue to run on the two remaining hosts. In total 2 X 160 GB = 320 GB of memory.

Someone any toughts on this?

Many thanks,

Remko
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Re: Memory overcommitment

Veeam Logoby Shestakov » Wed Mar 18, 2015 2:13 pm

Hello Remko,
remko.de.koning wrote:After investigating on the issue we noticed in the Veeam graphs that Veeam think that approx 200 GB is equivalent too 100% memory
Left side of the graph shows amount of GB memory. Right side of the graph shows Memory in percentage.
Why is Veeam showing the 200 GB as 100%?

Could you please specify where you see it? If you open Infrastructure View Tree in Veeam One Monitor and choose the Hyper-V cluster what do you see under the "Memory" tab? Please provide a print-screen if possible.

In general the alarm is generated when the sum of free VM slots in the entire cluster is greater than the sum of slots in the largest host.
Thanks.
Shestakov
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Re: Memory overcommitment

Veeam Logoby remko.de.koning » Wed Mar 18, 2015 3:14 pm

This is a screenshot of the memory of HyperVisor 1
Image
The total memory of this server 160 GB

Notice the right hand side is at 100%

The discussion about free slots I have read as well but am at a complete loss.
The largest VM I have is 20 GB of memory. As far as I can tell I have more than enough free memory space available.
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Re: Memory overcommitment

Veeam Logoby Shestakov » Thu Mar 19, 2015 1:18 pm

I see where you concern is coming from. Let me discuss this with developers to clarify the logic.
I`ll write back once I have the information. Thanks!
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Re: Memory overcommitment

Veeam Logoby iHire » Thu Mar 19, 2015 3:09 pm

We are having a similar issue in our evaluation of Veeam ONE. Veeam ONE is reporting a Cluster Memory Overcommitment alarm, but our VMs are using a total of only 696.12 GB (45.15%) of memory as reported by the Memory Performance Chart and graph, when our cluster has 1152GB installed.

We have a four-host Hyper-V cluster (Windows Server 2012), supporting 80 VMs, with cluster reserve set to 1 (meaning the cluster will support all VMs if one host is offline). Each host has 384GB of memory, so the cluster's supported total memory is (4 hosts x 384GB) - 384GB = 1152GB.

Our two largest VMs are using 32GB each, with the next 10 largest at 16GB, and the next 12 at 12GB. The other 56 range from 8GB down to 2GB each.

Additionally, we use Microsoft's System Center Virtual Machine Manager 2012 (SCVMM). VMM has reported no cluster overcommitment. And, if we add our SCVMM server to the Veeam ONE Monitor, the same cluster shows no overcommitment alarm. The alarm is only seen when Veeam ONE looks at the cluster directly.

It's my understanding that SCVMM 2012 has greatly improved algorithms over previous versions for determining overcommitment status. I'm hoping that Veeam ONE is not using algorithms similar to SCVMM 2008 which often falsely reported overcommitment.

We like the Veeam ONE product, but this could be a deal breaker in our evaluation if we can't fully trust the alarm capabilities.
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Re: Memory overcommitment

Veeam Logoby Shestakov » Fri Mar 20, 2015 2:33 pm

Going back to the screenshot you provided,
looks like the Memory Usage graph is a green one and shows approx. 40% as expected.
While Blue line shows Hyper-V Services Memory Consumed. Am I right?

Regarding the Memory overcommitment alarm, we are currently inspecting the logic with developers for the purpose of possible inaccuracy.
Once we are done, I`ll posts our findings here.
Thanks.
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Re: Memory overcommitment

Veeam Logoby remko.de.koning » Tue Mar 24, 2015 9:39 am

Thanks, really appreciate you guys looking into this!
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Re: Memory overcommitment

Veeam Logoby Shestakov » Tue Mar 24, 2015 10:15 am 1 person likes this post

We confirmed that in some particular cases like yours the alarm may be triggered earlier than it should. We`ll revise the behavior in future releases.
Thank you for mentioning it!
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Re: Memory overcommitment

Veeam Logoby remko.de.koning » Wed Mar 25, 2015 8:47 am

Thanks for your efforts! Much appreciated.
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Re: Memory overcommitment

Veeam Logoby Shestakov » Mon Mar 30, 2015 4:19 pm

You are welcome Remko,
Once you have a question or suggestion please let us know!
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