Most encountered backup issue

Guess what most of the issue you will see on backup.  Name resolution and drive ordering.
I can say 70% of the time related to name resolution.  If you tell them it is DNS, they will answer you no.  Add it to host table, it works.  Guess what, different DNS server gives you different result. However, they will keep on telling you it is not their DNS server.
The other issue is drive ordering.  How come some of the drives do not start backup?!  The drive ordering is not correct.  Most of the time due to reboot.  For example, drive with SN 501 is configured as \\.\Tape0 (the first one) then drive with SN 502 is \\.\Tape1....  After reboot, now, drive with SN 502 is discovered first and become \\.\Tape0.  When you attempt to mount a tape on \\.\Tape1, (because the order the drives discovered is not the same, \\.\Tape1 is discovered first) you will get an error eventually.  If you are using FC Tape library, configure persistent binding!!!  Otherwise, you will end up wasting time to reconfigure your library everytime you reboot your backup server.