With the advent of RAID technology, disk drives have a virtually unlimited capacity and are very resistant to media failure. Hard drives also offer a read and write speed orders of magnitude beyond even striped DLT drives.

The most common method for utilizing disk backups is to backup your databases and transactions logs to the local disk drive. This offers simplicity in the backup and also the fastest backup method available. This is because you are only limited by the transfer rate of the disk controller. It does place a burden on local storage space. It also leaves you vulnerable in the case of a complete server crash or multiple disk drive crash.

The primary reason to take backups is in case of a server or multiple disk drive failure. You want protection in the case of a failure. Since the failure will be on the machine SQL Server is running on, you might not want to backup to the local disk. In this case, you can backup to another machine on your network. This offers a slower backup rate than to the local disk, but is still faster than tape backups. In order to lose the backups, you would need to have more than one server crash or have multiple drives crash on two machines simultaneously. If this happens, you can bet there are more severe problems in your server room than just these two servers crashing

If you are choosing this option, try to dedicate a server for backups. Many people are tempted to utilize space on a PDC or a BDC. This is generally frowned upon. The PDC and BDC play specialize and vital roles on your network. You do not want to affect their stability by introducing something that is not related to their function. The best option for a separate backup server is a relatively low end box, small amount of RAM, large storage capacity, redundant RAID controllers with battery backup, and fiber connections. This server does not need a large amount of RAM, because its primary purpose will be reading and writing data. Therefore you want to maximize all of the components related to the disk drives.

This section would not be complete without mentioning the other types of media you could encounter. Tape and disk are by far the most proliferant media used. You can also use CD-ROM, removeable storage such as Zip and Jaz drives, optical drives, and magneto-optical drives. These storage types can be ultilized, but are very uncommon. Magneto-optical and optical drives are very specialized devices that you might only encounter in the largest enterprises due to their high cost.

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