Backup Window and Amount of Data

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Overview

The next step in developing a backup and recovery strategy is to determine the storage media requirements. Based on the information you have already gathered, you should have a pretty good idea of how much data is going to be backed up, how many copies you will need to keep, and how long you will keep them. All of this information figures into the total storage media requirements. If this is a new backup domain, you can use this information to determine what type of tape drives and media will work best. If this is an existing domain, you can determine if you have enough drive and library capacity.

As you no doubt have already figured out, this is not an exact science. Every piece is interrelated. The size of the servers is dependent on the number of drives. The number of drives is dependent on the amount of data being backed up and the backup window. The backup window is related to the number of drives and the speed of the drives. The ability to use the bandwidth of the drives is related to the network speed and layout. That is why we picked a starting point of analyzing the data and moved forward from there. You will need all the data gathered using the guidelines in the first three chapters before proceeding.

As you move forward with evaluating storage media, you need to consider the selection of a suitable drive technology. The number of different drive types and the number of different libraries that support the different drives complicate this decision. You should gather enough information to make an informed decision. One place that can provide a comparison of all the different types is www.storagemountain.com/hardware-drives.html. This Web site shows all the different technologies and gives speeds, capacities, and load/unload times, as well as access times. All these figure into the final decision. If backup speed is the primary concern, a fast drive with a high-density cartridge might be the best solution. If recovery speed is more important, you might want to look at a fast drive with fast access, but high-density may not suit your requirements. If you want to recover a single file from the end of a tape, it would be faster to find it on a 20-GB tape than a 120-GB tape.

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