As one of the new let’s call it minor enhancements, Veeam introduced the possibility to process VMs and/or VMDKs parallel within a single job. I have to admit, this is one of my favorites simply because it further improves backup scheduling.
If you upgraded from a previous Veeam release like 6.5 you will need to enable the parallel processing feature within the Veeam console
Once it’s enabled, all virtual machines within a job will be processed parallel.
There are two possible reasons for this behavior. Either your backup proxy or your backup repository settings limit the number of concurrent tasks. Just klick on the virtual machine which is still in “Pending” state to get the information which resource is not ready.
By default, if you haven’t changed the number of concurrent tasks on your backup repository, only 2 VMs/tasks will be processed simultaneously. The number of concurrent tasks can be easily changed within the repository settings, but make sure your repository offers sufficient I/O performance & throughput to really make use of the parallelized processing.
The reason for this one is the “max concurrent tasks” option on your backup proxy. This still limits the number of parallelized tasks. Of course you can increase the number, but make sure your backup server/proxy has sufficient computing resources (CPU/RAM) to handle more than 2 tasks.
Your backup server/proxy has to read, write, dedupe & compress all the data which requires computing resources in the end.
As you can see, 2 concurrent tasks are able to fully utilize 4 virtual CPUs as well as a bunch of RAM. If your backup server has to handle too much concurrent tasks or lacks in computing resources, the backup speed will suffer.