In strategy number 1, you are still vulnerable to media failure if the disks fail and the tape happened to be bad. This is extremely rare, but Murphy’s Law says that it will occur if you have a database crash.

A better implementation also puts a much greater load on your server and resources. This method utilizes a simultaneous dump to both a local tape device and to disk. This means that you now have the same backup stored on both disk and a tape.

The disk offers the same advantages as in the first strategy. The tape backp offers the same level of media protection. This one adds to that protection by also archiving the disk backup to an additional tape. This canbe done to a second tape drive locally attached, but is normally done to a network tape drive by means of UltraBac, ArcServ, and Backup Exec.

In order to lose everything, you now have to have the disks crash and have two bad tapes all at the same time. This is even more rare than in the first case.

Backup Strategy #3

These last two strategies are the ones I prefer the most. Due to the low cost of hardware, dedicating a server as a backup repository is well within the means of any company. You would specify a low end server in terms of RAM and number of processors. This server should be maximized for storage space and read/write throughput. A good class of server to use for this purpose would be equivalent to a Campaq 1850.

With the previous implementations, you are vulnerable to a server crash. Because your backups are loaded on the local disk array, you are particularly vulnerable to this. If your server crashes, the disk drives are normally the first to go. This leaves you relying on your tape backup.

To avoid this, redirect your disk backup to a backup server. Just as in the previous strategies, the backups are then archived to tape for media protection. In order to be forced to resort to tape, you would have to lose two machines. If this happened, you are normally worried about a more major problem in your server room than just these two machines.

This backup server also becomes a focal point of your Enterprise backp solution. You can redirect all of your database, messaging, groupware, etc. backups to this server. This allows you to invest once in a single piece of hardware to server many needs throughout the organization. This server is also the only one that generally has a tape device hooked to it, thus saving a significant amount of money on purchasing tape devices for every server. It also allows you to more efficiently manage your tape media since you will waste much less space on tape with this solution.

Backup Strategy #4

The final strategy is really a combination of number 2 and number 3. This also puts an additional backup load on the server. Here you would simultaneously backup to both the local hard disk and a network backup server. Each of these backups would then be archived to tape. This gives you two disk backps and two tape backups. The only way this one could fail is if the disk arrays on two separate servers crashed and both tapes failed simultaneously. This will almost never happen and is about the highest level you should ever need to go to.

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