Reducing Concurrent Number of Backups for UEBs



To inform Xen UEB users about concurrency of backups running on Xen UEBs.


Running multiple Xen virtual machine (VM) backups on Xen UEBs can sometimes cause the Storage Repositories (SRs) in the environment to fill up due to the way the SRs are designed in the Xen environment.


Unitrends creates snapshots of Xen VMs to perform backups of those VMs. These snapshots exist throughout the course of the Xen VM backups and can take up space equal to that of the size of the disks of the VMs that are being backed up. This can in turn cause issues about SRs being filled up and can lead to failed backups of the VMs or can even cause false SR filled up alarms. More information related to Xen snapshots behavior can be found in Citrix XenServer's Knowledge Base article below.


To resolve this issue, you have two options:

  1. Reduce the number of concurrent backups that the UEB appliance will perform, thus reducing the number of snapshots - and space used - on a given Storage Repository.
  2. Protect some - or all - of your VMs with an agent, which eliminates the need for XenServer snapshots altogether. For example, if one VM's snapshot takes up the majority of an SR, you can put an agent on just that one VM and use hypervisor protection for the rest.
If you use option #1, you will need to calculate (or estimate) the number of concurrent backups your SRs can support. To do this, please see the Citrix KB article below to understand how snaphshot space is consumed for your particular storage. Then, determine the minimum number of concurrent backups you can perform across all SRs that are protected by a single UEB appliance.

You can use the following procedure to set the number of concurrent backups you want to perform. Note that this setting is global for the entire UEB virtual appliance:

1. Go to the Unitrends legacy UI by browsing to https://<UEB_IP>/recoveryconsole.
2. Go to Settings > Storage and Retention > Backup Devices.
3. Click on the Storage Device that is being used for Xen VM backups.
4. Change the Maximum Concurrent Backups value to the desired number.
5. Click the Confirm button.

Note: The above steps also apply to all other supported hypervisors, as well as, the Unitrends agent backups

If there are multiple storage devices configured on the Xen UEB, this process needs to be performed for each of those devices.

Third-Party Sources

Citrix KB article explaining Xen VM snapshots -

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