Take a look at the storage management problem of very large databases. These systems typically consist of hundreds of gigabytes to multiple terabytes of storage. These are mission-critical applications that must be continuously available. Conventional backup methods are too slow and lack the reliability and scalability required by these huge systems. To illustrate this point, a company that decides it needs to backup a 1 TB database every night within a 5 hour window has a serious challenge.
Backup performance is measured in GB per hour and tape drive performance in MB per second.
The example of 200 GB per hour translates to 55.6 MB per second. No commercial tape drive is that fast. To solve this backup problem, it would take 12 transports operating in parallel. But, typical 3490 cartridges are only 2.4 GB in size. This means 420 pieces of media are needed for each backup, depending on the degree of compression achieved.