Mitigating low usb disk space error in backup scenario

Your strategy doesn't sound that bad to be honest, but the transaction logs not flushing does concern me somewhat. If you have other specific concerns about your setup, please edit your question to include them and I'll do my best to answer.

I read it that you're doing daily full backups. Depending on the size of your mailbox stores you might want to switch to daily incremental (i.e transaction log) backups instead of daily full backups. This will mean you complete your daily backups much quicker and they will consume less storage space, but this may not be an issue for you if you have small mailbox stores or the current backup window is acceptable.

Since you're using Backup Exec, make sure you are using the Exchange Agent. I won't stress that enough, since that's what does all the heavy lifting and makes sure your Information Store backups happen properly.

You say you're backing up all local volumes - specifically exclude the directories your mailbox stores and transaction logs live in from the file level backup. Hopefully Backup Exec won't be stupid enough to try and back these up.... but we are talking about Symantec after all!

As I said, I'd be concerned that your transaction logs aren't flushing. In the vast majority of cases this means backups are not completing properly, since the transaction logs are flushed after a backup. Check your Backup Exec job logs to see if your backups are actually completing successfully and investigate any warnings or errors. Your Exchange server should also log events relating to backups, so check out event viewer if necessary.

On a related note, make sure you do frequent Active Directory backups too. Exchange relies very heavily on Active Directory and stores an awful lot of configuration date in it.

I'll also do a quick spiel about your backups being effectively useless unless they are tested. I appreciate it isn't always possible, but if you can restore your entire environment (Active Directory and Exchange) to a completely isolated and different set of servers it will make you feel a lot better.

The answer is - buy netbackup. It shouldn't suprise you that there are 2 products from the same compqany with builtin limitations on at least one of them. Or live with what you have. the solution you came up with (and are aware of the implications of) seems reasonable. Yes it kinda sucks- thus change the limitations by changing the software (btw why do you need to stick with symantec?)