What Happens When No Swap Volume is Available?

Have you ever asked yourself that question?

A customer of mine a small number of VM’s on one host that were continuously crashing. He would power them up and within less than 5 minutes – they would get powered off.

In this case – the host had a swap partition configured not with the default setting but rather as a separate shared datastore.

Swap location

So what happened?

The swap_12 datastore was not accessible (the reason – is not relevant at the moment), and then they powered on a number of machines.

Going to the vCenter event logs showed this:


Notice that the error message is not that descriptive. Inside the guest OS there was no additional clues to the cause for the power off of the VM

But if you look closely you will see the last line mentions this -

*** VMware ESX internal monitor error *** vmk: vcpu-0:Unable to read swapped out pgNum(Ox27dca) from swap slot(Oxl000fb8a) for VM(1717757)
Which of course leads to the direction of the VMware Swap file not being available.
You cannot run a VM without an accessible Swap volume… Winking smile