By placing an intelligent controller between the mainframe and the tape devices, and attaching a large disk cache area from and to which data can be read and written, the host system is freed of the burden of managing the media. The intelligent controller handles the migration of data between the disk cache and the tape media in an optimal space and time fashion. The host system is presented with an image of many virtual tape devices with a more standard configuration. There are significant direct and indirect benefits of this VTS architecture. The data is actually being read from or written to disk, so there are immediate benefits in disk processing speed.
Disks are many times faster than tape devices, even the new tape technologies.
Many tape datasets are read soon after being written, typically within twenty-four hours. The disk cache on the VTS is sized and managed so that there is a very high probably that a dataset written yesterday will still be on the disk cache today, saving the time required to mount the tape. Clearly, wall clock time will be reduced for applications using the virtual tape mechanism. Another architectural feature of the VTS is the connection of the tape drives with an Automated Tape Library. This small cabinet houses all the tape media, and two robotic arms that fetch tape cartridges and mount them into the drives for use, then afterward, return them to storage cells.