Back-up Tape Rotations
How do I set up a tape rotation schedule?
There are many different ways to set up a tape rotation schedule, and a simple Google or Wikipedia search will give you detailed information on the options available.
The most simple rotation method, called First In First Out, involves sending backup tapes offsite on a periodic basis (daily, weekly or monthly) and having the oldest tapes brought back to you for reuse.
Typically, companies using the First In First Out method will have at least three backup sets, so that when the oldest set is brought back and exchanged for the most recent, the third set still remains offsite and protected.
The Grandfather-Father-Son rotation method may be the most commonly used method. It is similar to First In First Out, but includes the periodic creation of long-term archival data sets. Producing archival tapes allows recovery of data from much earlier time periods and also protects against situations where an undetected error is introduced and not discovered until much later.
Regardless of what method is used, the frequency with which backups are taken and sent offsite is determined by how much data your company can afford to lose. For example, if your company can't afford to lose more than 24 hours of data then you should send tapes offsite daily.
Full vs. incremental vs. differential
Whether each backup set contains full, incremental or differential backups is determined by the time required to backup your data weighed against the complexity of the recovery should you need to restore your data.
Full backups involve the most data and server downtime, but are the easiest to restore from. Differential backups involve lesser amounts of data, but the restoration process is more time consuming. Incremental backups involve the least amount of data, but the restoration process is the most cumbersome of the three options.