Question on Memory

[nasadmin]

HI

I have one question on memory. My Linux VM is showing that used memory is 16782MB, but ESXtop is showing that % of active memory is 8. My question is

1 .Should I look at used memory inside the VM or % of active memory in the esxtop to know the VM memory requirement while doing the sizing?

2. If I consider the VM memory requirement basing on the % ACTV parameter in the esxtop ,then what about the swapping happening inside the VM ? It will cause extra writes on the VMDK.

3 .How do I know what is the exact memory requirement for the VM? Should I say that my VM requires minimum 17GB or should I consider the 8% as the memory requirement and fine tune my VM to avoid swapping?

Please educate me .My apologies if it is repeated question

Thanks

[zXi_Gamer]

Always consider the active memory of the VM. Take a look at http://www.yellow-bricks.com/2011/04/29/which-metric-to-use-for-monitoring-memory/ its quite useful and also http://www.vmworld.com/docs/DOC-2116

[emma234]

Hi pratap533

In regards to you thrid question How do I know what is the exact memory ?  Its variable and depend upon appliation you are going to run on that vm

"He Conquers, Who Conquers Himself".

[rickardnobel]

nasadmin wrote:

1 .Should I look at used memory inside the VM or % of active memory in the esxtop to know the VM memory requirement while doing the sizing?

2. If I consider the VM memory requirement basing on the % ACTV parameter in the esxtop ,then what about the swapping happening inside the VM ? It will cause extra writes on the VMDK.

I am really not too fond of the Active Memory, since it is just a sample of how much memory the VM has touched in the last 10 minutes or something and does not really show how much RAM the VM does actually need. Most operating systems must load quite lots of drivers, services and similar into RAM and then the rest of system/application takes some amount. The operating system might not need to read/write into all this pages often, but if sizing from the "Active" then your VM is likely to suffer from heavy internal swapping.

[msundling]

Hello everyone

Disclaimer, I´m from a vendor but my intent is not to try sell you anything but to help you on this particular topic.

We have put together a lot of resources such as white papers and pod casts covering VM sizing.

I recommend you take a look at: http://www.vkernel.com/vm-sizing-resources

Best Regards,

Mattias Sundling
Evangelist - VKernel
A Quest Software Company