Max concurrent tasks in Veeam B&R

A quick post regarding max concurrent tasks in Veeam B&R which are tunable options in both proxies and repositories. The default max concurrent task for proxies is set to 2, for backup repositories the default is set to 4. An important thing to note is that we are limiting different things when configuring this max concurrent task between proxies and repositories.

When configuring proxies, the max concurrent tasks are based on a single virtual disk. So for example, if we had a single virtual machine with 4 virtual disks or a 4 virtual machines with a single virtual disk each, the units of resource scheduling required is the same, the units of resource scheduling required being 4 virtual disks that need to be processed.

If we set our proxy to 4 concurrent tasks then we could process all 4 of the virtual disks concurrently.

When configuring Backup Repositories, the max concurrent tasks are based on per-backup files (.vbk, .vib & .vrb). If you use non-per vm¬†backup files in your backup job it’s always going to be a single task for the whole job, if you use per-vm backup files each VM in the job is going to have its own backup file.

If we set our repository to 4 concurrent tasks then we could only process 4 backup files (vbk, .vib & .vrb) concurrently.


3 thoughts on “Max concurrent tasks in Veeam B&R

  1. Oscar Levi

    Great. thanks for clarification, now all stay me light. I am prepare myself for VMCE 9.5 and this is very well.

  2. NMR

    I read concurrency available for Backup Proxy and Backup Repository. Does the concurrency applicable for Data mover available in Veeam hyperv integration service too?

    Also assume I am having multiple VMs in a backup job and I have a backup proxy which could process 8 tasks concurrently and my backup repository can only process 4 tasks what will happen (assume I am using per-VM backup chain).

    My assumption is 4 VMs will run in parallel because of the backup repository limit, is it correct?

    1. admin Post author

      All backup proxies and backup repositories in the backup infrastructure can have task limitation settings configured for them.
      The Hyper-V on-host and off-host backup proxy task limits are configured when adding the proxy, see picture below;

      When you start a data protection or disaster recovery job, Veeam Backup & Replication analyzes the list of VMs added to the job, and creates a separate task for every disk of every VM to be processed.
      Key word is disk, not VM. Each disk being processed consumes a task on the proxy and repository.

      The Veeam Backup Service detects the number of tasks that required backup infrastructure components are currently processing, and analyzes the number of allowed tasks for these components. If the number of currently processed tasks has reached the allowed limit, the backup infrastructure component will not start processing a new task until one of the currently running tasks finishes.

      Meaning if you have multiple VMs in a backup job, a backup proxy set to 8 tasks and a backup repository set to 4 tasks then only 4 VHD’s (VM disks) would be processed concurrently.



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