Monday, July 28, 2008

Monitoring VMFS disk space

I always thought that monitoring free space on VMFS volumes was not useful, but I was wrong. If one creates a snapshot of a VM, and forgets to remove this snapshot after a while, the VMFS might become full and some VMs will crash.

So... how can it be monitored? Well under ESX the quickest solution I found is writing a script, called from a key-authenticated SSH that is executed by Nagios.

I'll spare the nagios side, but here's my generic script that runs on ESX. It uses "vdf" which produces df-like output for VMFS volumes. Of yes, it's not executed as root but as some other unpriviledged user that calls vdf via sudo:

N.B. Installing NRPE in ESX is a venture I will not consider. Many people in the forums tend to have problems with this, and it would take too much effort. SSH works right out of the box, is more secure, and does not require me to install third-party software in the ESX console (except my script).

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