Virtual machines swapping memory, high I/O wait time. vCenter not reporting it

[max08]

Hello

I am running into an issue where users are complaining about memory swapping on their virtual machines.  I can see swapping occur inside the guest but I dont see any reports of it via vcenter.  Currently we are using a kernel that requires a patch to get it fully working.  Could that explain why I am not seeing what the guest are seeing?

With the swapping users are complaining of high I/O wait time as well. However I am having a hard time pin pointing where the problem is.

There is no latency to the SAN, davg/wr is right around 1.0 and guest memory useage reported via vcenter is hovering around %30.

Example:

guest (3GB):

Mem:   3085028k total,  3001496k used,    83532k free,     6088k buffers

Swap:  2097148k total,  1449116k used,   648032k free,    55160k cached

             total            used           free     shared    buffers     cached

Mem:          3012       2931         81          0          9         62

-/+ buffers/cache:       2860        152

Swap:         2047       1431        616

vcenter:

3.06 GB consumed

1.35 Active

0 swapped

Any ideas would be much appreciated.

Thanks

[weinstein5]

Ty[ically if swapping is occurring inside the guestis an indication on one of two things occuring -

1. not enough memory is assigned to the guest - to correct this increase the memory assigned to the VM -
   
2. There is contention for memory on the ESXi host and the Balloon driver has been activated -- this can be checked by monitoring balloning activity for the VM
   

[max08]

Other than looking at vcenter how do I monitor balloon activity?  Because right now its not reporting any.

[weinstein5]

you would be able to set an alarm within vcenter to send an email if balloning occcurs - you could also monitor the vmware tools activity within the VM itself since VMware tools is where the Balloon driver is installed -

But back to your original question without balloon activity it sounds like there is not enough memory assigned to the VM -

[mittim12]

Just to add to what weinstein5 has said the swap counter in vCenter does not reprsent the same swap that you see inside a guest OS.    The swap in vCenter is monitoring vSphere swapping while inside the guest OS monitors OS swapping.