We are proposing the same definition set for tape using the categories of fault resistant and fault tolerant so that we communicate independent of drive technology. Figure 4 presents the architecture. Each level in the availability hierarchy is related to the system availability class defined in Figure 3. In contrast, the first failure resistant categories use multiple drives. If one drive is down, then the process can fail-over to an alternate drive.
Operations continue even if at a reduced rate.
The next level in the hierarchy is configurations using multiple drives in multiple libraries and RAID tape arrays built into libraries. Redundancy creates a degree of failure tolerance and we can truly talk about high availability tape systems. This hierarchy takes into account the reliability experience of the library community. Don't forget that good library management software is also essential. Our recommendation is to begin with understanding your availability needs.