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.