Free Space on Datastore

[1-0-1]

Just wanted to find out community impression based on experience as I know this can cause issue. We have a highly specialized virtual machine that is currently located on its own high speed datastore. The virtual machine is about 520 GB big and the datastore has about 15 GB free only. I cannot move it to a bigger datastore, switch it off, extend the datastore.

My question is will the replication and/or backup of that virtual machine not cause the datastore to run out of free disk space completely and thus will lock up the entire virtual machine. Is there a way one can estimate how big the snapshot that is being created during the backup and/or replication process will be or even relocate it on another datastore?

We using vShpere 4.1 (ESXi 4.1 hosts) and my question is for VEEAM B&R v6 or v5.

[veremin]

Veeam Snapshot doesn’t preserve memory state of your VM, thus it will start out at 0 GB and grow over time recording the block level changes to the virtual disk.

So, my answer for your question would be “it depends”. Primarily on the amount of changes that are likely to take place till the moment backup job ends (will the amount of them exceed the space provided or not). This number can be estimated roughly based on the IO rates of this VM.

Nevertheless, 15 GB seems to be inadequate in this situation. According to the best practices, it’s strongly recommended to have 10% free of datastore in case of general VM, and, at least, 20% in case of VM with high change rate (SQL, Exchange,etc).

Please also see this topic. It's definitely worth checking.

Hope this helps.
Thanks.