Excluding Backup Disk from Veeam

I came across this issue the other day whilst I was installing Veeam Backup & Replication 6 for a customer.  The issue was not so much about excluding a disk from the Veeam backup but excluding the Veeam backup repository disk from a backup.

This is the story of the situation, the reason for the issue and then the solution to the issue:

The Situation

We had just finished installing a new ESXi environment for the customer and were just configuring a Veeam backup.  The customer had an unusual requirement to split their OS disks and Data disks onto different speed disks… this is a little unusual but is perfectly valid.

They had Veeam installed on a virtual machine on the ESXi environment and had presented up a 2TB disk to the Veeam virtual machine as the storage drive for the backups, this was then going to be used as the Backup Repository.

The customer then explained that they wanted to backup the Veeam virtual machine (excluding the Backup Repository disk).  This seemed like a reasonable request and therefore we went through and configured the backup task and performed the first backup… the backup failed with the following error message:

Error: File <unspecified filename> is larger than the maximum size supported by the datastore <unspecified datastore>

The Reason

I’m not completely certain of the reasoning behind the error message but I believe that the issue is due to the configuration of the virtual disk and the way that VMware performs its Snapshots.  Within Veeam we had excluded the Backup repository disk from the backup as normal but obviously this meant that it was still part of the configuration on the virtual machine.  When Veeam performs its backups, it takes a snapshot of the virtual machine… but unfortunately, cannot choose which disks to be snapshotted and has to apply a snapshot to the whole virtual machine.  This meant that there was not enough space available on the datastore where the configuration files are stored to house the snapshot files and therefore the error message above appeared.

The Solution

I performed some investigation on the subject and was racking my brain about how to solve this issue and then remembered a feature of VMware that I knew about but hadn’t really used before.

To avoid the 2TB disk used for the backups being included in the snapshot I went through and enabled the option on the disk to make it ‘Independent’ and ‘Persistent’.  This excludes the disk from being snapshotted but makes sure that the data is still written directly to the disk.  The unfortunate thing is that you cannot make the change to the disk once it is attached to the virtual machine… the thing to do, is to remove the disk from the configuration on the virtual machine (making sure not to delete the disk).  Add the disk back to the configuration of the virtual machine… making sure that the ‘Independent’ and ‘Persistent’ options are selected… the next time that you run the backup, it will complete successfully excluding the larger disk.