Using Backup Exec 2010 R3 on a Windows 2008 R2. Target server is Netware 6.5 Sp8 virtual machine running on a VMWare Esxi infrastructure. The server has 4GB RAM.
We are having a problem where our backups have started to slow down to the extent that we cannot backup our 3TB of data (on a single volume) which is on a san storage, over a weekend. Although I do appreciate that as our volume of data to be backed increases, so will the time that it takes to back it up, but recently there has been a noticeable slowing down of the back up rate. As an example, speeds that were once over 1000MB/min are now lower that 700MB/min. This makes a significant difference to the overall backup time.
We also back up this server to an off site TSM library. The owners of which have recently contacted us complaining that the backups have started to hog their system as well!

I've done some checking on the Symantec website and the main thing that I could find was a suggestion to 'SET TCP DELAYED ACKNOWLEDGEMENT=OFF' and 'SET TCP NAGLE ALGORITHM=OFF'. Unfortunately these were already set.

I don't know if it's related but I've had to cancel a Diff which had overrun (although this is becoming the norm now!). It was hogging the processor and slowing down user access. The guilty process was a 'VxNDMP..' file. I cancelled the backup and things got back to normal.

Are there any other standard Netware configuration changes or checks (memory management issues, more RAM, etc) that have been found which could make a difference in my situation? Have we reached a volume size that is to big for NW 6.5 to process at normal speed?
NB Our other main NW 6.5 server, which has 1.25TB of data, is able to backup at a rate of over 900MB/Min.

As ever any help is very much appreciated.