Monitoring datastore usage
When a VMFS datastore does not contain enough free space to efficiently operate, storage operations become fairly unpredictable and performance can suffer. We may experience things such as not being able to power on virtual machines, vMotion failures, poor or slow performance, and intermittent snapshot failures just to name a few. Needless to say, when we run out of space on a datastore, we will most certainly experience issues so we have to be sure that we always have free space available.
The question for us is how much free space do we need to have available? In KB article 1003412, VMware recommends that 200 MB of free capacity remaining be a threshold when we should take action. In practice, most vSphere and storage administrators would never let vSphere datastores get even close to the 200 MB threshold. The KB article 1003412 also states that a VMFS volume will only ever grow until there is 100 MB of free space. The 100 MB free space is a critical threshold...
