I presume that this is a tape that will be used in a backup of some sort. First thing to do is determine what kind of tape is used. Then I’d find the lowest or best for the money tape on the net. Do a Google to compare. Next you have to determine how much disk you are going to backup to tape. If you are going to use SDLT, they can now store up to 600Gb, uncompressed, depending on your tape drive. SDLT tapes can cost up to $100 per tape however. Once you know how much you are going to backup, see how many tapes it will take to back up everything once. Get that total, and bounce that against your backup stratagy. Hope this helps!