Question : Full Backup taking way too long

I have just implemenented a new 160 gb  HP tape dlvt tape drive. I previously had a 80gb tape drive same model which we are still using for incremental backup during the week.The software i am using is arcserve backup 11.1/ There is two jobs set up  1 an incremental which  goes to 80gb tape drive and a Full which goes to the 160 gb tape drive. The jobs seems to be working fine. The problem is the full backup is taken way too long. i.e i run this on friday night at 9:30pm and by monday morning it had only progressed 16 %. It is not major amount of data 80gb or so. Previously the full use to go to the 80gb tape drive and was working fine only problem was it was just a little under capacity get about 90 % data or so but easily within the time frame. ANyone any ideas why this is taken so long?? I have tried putting compress files before backup see if that would help but still the same . The server is windows 2003 the arcserve software is on.

Answer : Full Backup taking way too long

i figured out what it was in the end it was to do with the service account. I had the reset the password for the service account in ad as i did not have the original password for the account i thought i just had to specify this under the job schedule when i was creating the new job. I was able to validate account access to servers etc. But it has to be changed also under the server manager section of arcserve you go server manager>>>>admin >>> brightstor system account it can be reset in here. . I am suprised the backup ran at all considering there was conflict
thanks