Memory??

[Fozz]

I have a question regarding memory and Virtual Machines.

In an ESX 2.5 environment, I have allocated the Minimum RAM to a Windows 2003 VM as 128Mb and the Maximum to 512Mb.

Over time I can see (in Virtualcenter under the Performance tab) that the VM has a constant 512Mb granted but only between 150-200Mb is active at any given time.

Now, if I logon to the Windows 2003 VM I can view the Task Manager within Windows and see that there is over 700Mb in use, and the total RAM in the server is 512Mb.

So what gives?

How can Windows report over 700Mb in use day after day yet the Performance tab of Virtualcenter shows under 200Mb granted over months of history?

[bigvee]

Windows might be including the page file in the usage... Some apps go direct to the page file regardless of how much memory is actually available.

Just one idea not being able to see everything.

[Fozz]

Cheers for the reply but I don't think so.

The pagefile is over 3Gb's so that doesn't add up right.

I have to say I am a bit in the dark as to how ESX handles RAM even after reading some guides on it.

I have app developers asking for more RAM assigned to this VM even though VirtualCenter shows it as under utilized....

[bigvee]

Most likely java apps..... I have the same problem all the time.

The page file might be 3GB in total size but it might only be using a fraction. I think when windows reports memory usage it does physical + page (depending on where you look at it).

Does Windows only show that it has 512MB ram allocated?

2.5 reports memory differently than 3.0, stuff like memory overhead/esx swap isint included in the metrics.... I didnt think windows was smart enough to figure that out though.

Not much of an answer I know... but I know how you feel I had the same fight with app teams. After going to 3.0.1 some of the issue went away as performance was a bit better. In some cases I just ended up alloting more ram (oversubscribed the host the VMs were on) just for political reasons.

[Fozz]

That's EXACTLY where I am.

This is actually a development SQL 2005 server.

I am looking in the Task Manager and Windows is showing 512Mb installed and showing over 700Mb in use.

So the developers look at this and get all panicky.

I am trying to explain that the VM can pull on more RAM resource should it need it (does not appear to need any based on the Performance tab in Virtualcenter) but I was hoping for more info from these forums to back me up!

[bigvee]

You can try to get them to read the guides from VMware about how memory is handled, how it can request more, how it better utilizes the memory, etc.

Im surprised with SQL they are complaining about memory and not disk I/O. Its purely perception on thier end and Im not sure theres much we can do to convince them otherwise.

Maybe someone else can jump in and give more insight, I just know it was a battle I lost - with all the statistical data on my side, purely for political reasons. I got the last laugh though because I limited there access so they dont actually get all the resources "alotted" to them hehe. They never complained....