Backup Storage (8.0)


Learn about different options for backup storage


Backup Storage

Unitrends Virtual Backup can take advantage of storage available via the hypervisor (like iSCSI or Fibre Channel) or network storage (CIFS or NFS shares) to store your backup data. When you deploy a Unitrends VBA, you configure the backup storage by either adding one or more virtual disks to the Unitrends VBA virtual machine or by specifying a network storage location (either an NFS or CIFS share).

When using attached disks, they can be created on local or shared hypervisor storage. Using a virtual disks attached to the Unitrends VBA is the recommended method for storing your backup data.

Backup storage is assigned automatically when you create a backup job. Multiple factors are used to determine the most appropriate storage, including location, existing backups, and the workload of the appliance. You can also define which backup storage to store VM backups on using the Protect page, Settings tab options.



The CIFS service account must have full permissions (read/write/delete) for the share used as the backup target. Also, antivirus software should not be configured to analyze or scan the Unitrends VBA CIFS storage repository.

NFS Shares

The Unitrends VBA requires direct write access to the NFS export. During backup, the Unitrends VBA will directly mount and copy files to the NFS share. It is important to configure the export to allow this behavior. The following is an example export line: /export/share * (no_root_squash,insecure,rw,sync)

How much storage do I need?

Due to data deduplication and compression, you can store, on average, one month of backups for each VM by allocating backup storage equal to the total size of the VM data you would like to back up. For example, if you have 500 GB of virtual machines, you should allocate at least 500 GB of storage space. Additional details on determining how much backup storage space you will need can be found the white paper Backup Storage Sizing Guide available on the Unitrends web site. For even more information and scenarios, refer to the Unitrends Virtual Knowledge Base.

Your backup retention policy determines how many backups are kept for each VM. Retention settings can be configured using the Retention tab in the Unitrends Virtual Backup Console's Configuration area.

Hard Links and Virtual Full Backups

A hard link is essentially a reference to a file or directory on a file system. Unitrends Virtual Backup makes use of hard links when deduplicating Virtual Full backup data on the backup data store. Because of this, hard links must be supported and enabled (if necessary) on any storage device used as a backup target for Virtual Full backups. By default, most storage device file systems support hard links and have them enabled - if your storage device supports hard links but does not have them enabled, refer to your vendor's documentation for details on enabling them.

Note: Storage used for Full/Incremental backups does not require hard link support.

If hard links are not supported or enabled for your backup storage location, a warning message is logged after defining the backup storage and restarting the Unitrends VBA. If you attempt to run a Virtual Full backup with storage configured that does not support hard links, you will encounter the following error, BDS incompatible with virtual-full job: Hard links are not supported.

Backup Storage Notes

  • In most environments, using an attached virtual disk to store backups will result in the best overall performance.
  • Backup storage cannot be shared by multiple Unitrends VBAs - each VBA must write to its own unique backup data store. When using multiple Unitrends Virtual Backup Appliances with network storage, the same backup target destination can be used if you create separate shares for each appliance. For example, you could send backups for UVBA-1 to \\StorageServer\backupshare\vba1 and send backups for UVBA-2 to \\StorageServer\backupshare\vba2.


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