Datastore filled up and VM crashed during Veeam backup

[jmoney]

Today I was running Windows defrag in my Vsphere 5.5 VM guest (not realizing this grows the virtual disk) and running a Veeam backup at the same time on this guest. Guest VM suddenly went offline and said datastore was out of space in Vsphere client. VEEAM finally stopped too, probably because it was unable to access the DNS name of our NAS (DNS being hosted on the guest that crashed).

I managed to delete a couple of ISOs off the datastore and the VM magically came back online after I had it retry (guest OS never crashed).

A couple of days ago VEEAM started warning me with this message I should not have ignored: Production datastore datastore1 is getting low on free space (81.4 GB left), and may run out of free disk space completely due to open snapshots.

Digging around, I now see in the Snapshot Manager a "VEEAM BACKUP TEMPORARY SNAPSHOT" that apparently can be deleted. Is it safe to delete that?

I've provided a screenshot here showing the datastore folder for this particular VM. Can anyone give me a sense of what's going to happen when I delete the temporary snapshot? http://imgur.com/a/KgsjK

What makes me curious is our datastore has not grown much at all in the last year. We've not added new VMs or lots of files to guests. I'm just wondering why it suddenly started running out of space.

Obviously I need to catch up on how these technologies are working and apply some best practices.

[Gostev]

Yes, it is safe to delete. The snapshot contains the latest VM disks state, and deleting it will merge the latest state into the base VMDK.

[jmoney]

Thanks. Deleted and all is well aside from needing to shrink the thin disk after zeroing space.