Backwards computability is extremely important in tape backup, due to the fast growth of storage capacities. Any tape solution you are using now will inevitably outgrow itself as your organization builds it data warehouse, so you want to make sure that your old data cartridges will be readable by your next drive. Choosing A Backup Tape Capacity is always referred to as compressed capacity on a single cartridge. This is basically how much the tape will hold. Backup Window is basically dealing with time.
Some formats are faster than others.
A solution that doesn't fit your backup window can jeopardize your backup rotation and your employees' productivity. Migration Path is very important also. Ensure your vendor and tape format has a clear path outlining future versions of the format. There are many backup systems out there. These drives are usually SCSI devices.