When taking a backup with Veeam Backup & Replication, a VM snapshot is created to get a consistent state of the VM. The snapshot is taken prior the backup, and it is removed after the successful backup of the VM. The snapshot grows during its lifetime, and you should keep in mind, that you need some free space in the datastore for snapshots. This can be a problem, especially in case of multiple VM backups at a time, and if the VMs share the same datastore.

Last week I had an interesting incident at a customer. The customer reported that one of multiple Veeam backup jobs jobs constantly failed. [caption id=“attachment_3734” align=“alignnone” width=“640”] jarmoluk/ pixabay.com/ Creative Commons CC0[/caption] The backup job included two VMs, and the backup of one of these VMs failed with this error: Error: Failed to open VDDK disk [[VMDS-SAS-01] VMDC1/VMDC1_1.vmdk] ( is read-only mode - [true] ) Failed to open virtual disk Logon attempt with parameters [VC/ESX: [vcenter.