I am backing up 11 physical servers with a Dell PowerVault 124T with LTO3 tapes. I used the wizard to set up a daily differential, a weekly full, and a monthly full. The job starts at 11:00PM and doesn't end until 9 the next morning. ( a full 10 hours). This seems like a lot for just 205 Gb of info. Also, I made sure that I checked the box to allow backup of open files, and it seems to be skipping these during backup.
Could be skipping files if those files are on BE's Active File Exclusion list...so files like *.edb, *.mdf etc.
For the slow backups, there are various reasons: # of files, slow network, type of backup device etc.
So how many files are you backing up? Small files tend to make the backup run slower as the tape drive won't spin up to its full speed for example. An antivirus actively scanning the BE services during a backup is another culprit.
You can take a look at the TN below which might shed a bit of light on things:
If you check the Alerts Tab, is there one to remove the media? If so, the job clock will keep running until you respond to that alert
You can setup an AutoResponse see the Admin Guide, page 638 or
You should expand your joblog and look at the timing for each of the resources that is backed up. This way you can narrow it down to which of your servers is causing the slow-down.