Risks of consolidating disks

[mu1980]

The ESXI 6.5 host we have has two VMDKs attached to one VM, one is 2TB and the other is 6TB, both thick-provisioned.  There is one manually created snapshot (no backup software).  The snapshot VMDK for the 2TB VMDK is about 140GB and the 6TB VMDK snapshot is about 350GB.  We have no VM-level backup of either the snapshot files or the parent VMDK flat files.  The datastore that everything is on has 2TB free.  The host is at Limestone Networks.

For performance reasons I want to consolidate the disks, getting rid of the snapshots.  How big of a risk is it to consolidate the disks?  Is it riskier to do the consolidation with the VM on or off?  I don't want to do it without a backup of the VMDKs, but is it really a risk not worth taking?

My thinking is the only way to reasonably quickly make a backup is to have Limestone attach a NAS to the same network this host is on and then use SCP to copy the flat file and snapshots to it.

And a related question: is the risk when consolidating more to the parent VMDK or to the snapshot or are both at risk?

Thanks!

[Devi94]

There is no risk in consolidating. It is advised to do consolidation in power off state or outside business hours, as it affect performance on the VM's.

[mu1980]

Really?  Assuming the consolidation process is not interrupted is there really no risk?  I'd still be nervous about it without a backup copy of the VMDKs.

[SureshKumarMuth]

Snapshots process is matured now a days and we are not seeing much issues with snapshots what we had in older versions when there were some limitations (i.e free space in datastore etc)  also you have only one snapshot each disk, so consolidation wont be an issue and no risk in it.

To consolidate the disk faster , you have to do it during off business hours when the load on server is less or when the VM is in powered off state. The risk level is high when the size and number  of snapshot is more. So take a prompt action to consolidate when the size of snapshot is less.

If you still think it is a risky one, rather taking a backup, you can clone the machine to another datastore which has enough space, so that even if the clone fails your original VM will be there. Once the clone is done, you may power off the old VM and start the new cloned machine. By this method you are saving time and 100% risk free.

[a_p_]

As long as you don't run out of disk space (which should't be the case), or disrupt the consolidation there's basically no risk in consolidating snapshots.

Creating , and deleting snapshots is a main function that's very reliable, and that's used by most VM based backup applications.

Unless the underlying storage is really slow, and I/O requirements for the VM are very high, I don't see a reason why you shouldn't run the consolidation with the VM being powered on.

André

[arieldaveport]

It's all about the storage performance. I recently commited a snapshot that was similar in size and the connection to a single iSCSI san were not up to the task and it stunned the VM multiple times during the commit. It lasted about ~1 hour and was unusable for about half of that. That being said the iSCSI network was really subpar.