Depends....don't you hate that answer? The number of tapes required to backup your data depends on two factors; one, the amount of data you are backing up, and two, the tape capacity you are using. If the amount of data exceeds the tape capacity then you need a tape drive that can handle this amount of data. This will require new hardware and new tapes. As an option, and this also depends on the tape drive model you are using, you can have the tape drive compress the data before it writes it to the tape saving you tape space. You may also run an Incremental backup as opposed to a full backup but you MUST run a full backup once a week, and then run Incremental backups the other days. Seems to me that you need to evaluate your tape backup needs and find a proper solution. Hope this helps.
