I have a production server (2008R2) that runs nightly fullbackup at 8PM. The duration is from 1 to 5 hours.
Now we are thinking about to move the back up to a later time due to performance issues for couple key nightshift useres.
The server has dozen of agent jobs scheduled starting around 1 AM. They typically complete in couple minutes. These are ssis packages moving data in and out.
Now my question is when full backup overlaps with these jobs, what will hapen? If they just run a little longer, that should be fine.
Theoretically the jobs can run simultaneously. The backup process does not lock any tables or other database objects. So you will not run into any resource contention issues on that front. What you might run into is disk i/o contention because of the reads and writes involved in the full backup. You will have to experiment to see if it really causes a problem. If at all possible I try to avoid backup jobs coinciding with other critical jobs.
Another possibility that you might consider, especially if your database is mostly read and only few writes is to do the full backup at a less regular interval (for example weekly) and do a differential backup each night. The differential backup will be larger and larger each night until you take the next full backup. Again, you will have to experiment to see if that makes sense in your scenario.