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morrisos
Contributor
Contributor

VC memory stats show lower utilization than Windows task manager

I know this has been asked before but I was hoping for a good clear reason I can tell another group in IT.

VM is a Windows 2008R2 16GB RAM, 4 vCPU running SQL, SSIS,etc. SQL max limit is 12GB.  Lots of SSIS activity.

Windows task manager shows total RAM utilization with SQL Server engine using 5GB and SSIS and other processes using the rest.  CPU usage is moderately high.  Server is bogging down.

VC stats shows VM only using around 6GB and lower CPU usage too.  Big discrepancy.

Bottom line is VMware admin won't add resources because VC stats show much lower utilization than Task Manager. 

How best to explain that VC stats don't tell whole story and we probably need to move host or something to have more shared resources available.

Anyone have a good clear explanation or documentation I can use?

Thank you,

Mpls DBA

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vXav
Expert
Expert

The active memory that you see in vCenter is very misleading when dealing with db boxes storing content in memory.

The active memory is actually an estimate of the guest's working set based on a sample of the pages accessed without guest awarness.

Long story short, if you have 30GB of db stored in RAM but your instance only accesses like 2GB over the last 5 min (for example), ESXi will see only 2GB "active" so you'll see something like 2GB active + OS overhead.

See this article for detailed explanations, you can share it with your VMware admins. They should be aware of that stuff.

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