Concerns about observed ballooning stats

[EdZ]

I recently gathered some statistics on the ballooning occuring in some VM's, and I was wondering if anyone has feedback on the numbers that I am seeing. I created a PowerCLI script and used the mem.vmmemctl.average statistic to measure the average and maximum values of the balloning on several VM's. Some of the values observed were quite high, and I'm trying to understand if this is a problem and if so how severe it is. Here are some of the statistics for the previous week:

VM1

Average vmmemctl: 4.8 GB

Max vmmemctl: 5.4 GB

Configured RAM: 8 GB

% Memory Ballon vs RAM max: 65%

% Memory Ballon vs RAM avg: 58%

VM2

Average vmmemctl: 760 MB

Max vmmemctl: 1.3 GB

Configured RAM: 2 GB

% Memory Ballon vs RAM max: 65%

% Memory Ballon vs RAM avg: 37%

Interestingly, it seems that the ballon driver never uses more than 65% of the configured RAM on the VM. I'm wondering why some of these VM's would have such sustained high values of ballooning? I thought the balloon driver would deflate after a while - the memory usage on the ESX hosts involved is only up to 89% according to the %Memory value from the hosts view in the VC. I thought ballooning would only kick in under very high memory usage on the ESX host too - it seems to be happening even when the memory usage is below 90%.

Thanks,

Ed Z

[ealaqqad]

Hi,

Usually ballooning happen when a VM need extra memory where ESX does not have a readily free memory for it, but it has other VMs that had that memory allocated to it but its not utilizing it. Rememeber when a VM request an amount of memory ESX usually give it that and never request it back althought it might be not using it utilizing the ballooning driver till it require it for another VM. Having high ballooning might be a bad thing if you are highly over commiting in your enviornment, else it might be just normal ESX operation giving VMs the memory it needs when it needs it.

Regards,

Eiad Al-Aqqad

Technology Consultant @ VMware

b: http://www.VirtualizationTeam.com

b: http://www.TSMGuru.com

[MKguy]

Ballooning can also kick in when you have a memory limit set on VMs. Make sure you don't have a limit lower than the allocated memory set on those VMs. Also, are you seeing any ESX-side swapping occur?