Library Robotics: Are Two Better Than One?

Tape libraries continue to improve in reliability and availability, in part because of new designs that incorporate component redundancy, along with other factors such as easy maintenance and proactive reporting.

Redundancy supplies a failover capability that is important to library reliability. However, it's important to identify when a component is truly redundant, or whether it is duplicated for another reason that has nothing to do with redundancy. This approach means that you cannot simply assume that, because the library has two of them, the components are truly redundant.

For example, dual robotics were not added to libraries for redundancy; rather, they were added for speed. As recently as a decade ago, robotic speed was important. But improvements in tape drives, library mechanics, and storage density have made robotic speed irrelevant. While backup speed is still important—maybe more important than ever—robotics are no longer a bottleneck.

It is quite likely that, instead of increasing reliability, the added complexity and components involved in dual robotics may decrease, rather than increase, reliability—depending on the design intentions.