Unix Backup and Recovery

Automated Backup Hardware

So far this chapter covers only the tape and optical drives themselves. However, today’s environments are demanding more and more automation as databases, filesystems, and servers become larger and more complex. Spending a few thousand dollars on some type of automated volume management system can reduce the need for manual intervention, drastically increasing the integrity of a backup system. It reduces administrator frustration by handling the most common (and most boring) task associated with backups—swapping a volume.

There are essentially three types of automated backup hardware. Some people may use these three terms interchangeably. For the purposes of this chapter, these terms are used as they are defined here:

Stacker

This is how many people enter the automation market. A stacker gets its name from the way they were originally designed. Tapes appeared to be “stacked” on top of one another in early models, although many of today’s stackers have the tapes sitting side by side. A stacker is traditionally a sequential access device, meaning that when you eject tape 1, it automatically puts in tape 2. If it contains 10 tapes, and you eject tape 10, it puts in tape 1. You cannot tell a true stacker to “put in tape 5.” (This capability is referred to as random access.) It is up to you to know which tape is currently in the drive and to calculate the number of ejects required to get to tape 5. Stackers typically have between 4 and 12 slots and one or ...