Monday, May 18, 2009


In the section on backing up and restoring files under Working with the System, we talked briefly about the process of backing up files and how to restore them. However, simply knowing what tools you need is usually not enough. You might not have enough time or space to do a complete backup, or restoring from a complete backup is not efficient. An advantage of doing a complete backup every day is that it is very simple. If everything fits on a single tape, you stick in a tape when you are done for the day and have something like cron schedule a backup in the middle of the night. If you have more than will fit on one tape, there are hardware solutions, such as multiple tape drives or a tape loader.

Rather that doing a complete back up every day, there are a number of different strategies that you can employ to keep your data safe. For example, one way is to back up all of the data at regular intervals and then once a day backup only the files that have changed since this full backup. If you need to restore, you can load your master back and one extra tape.

Alternatively, you could make a full backup and then each day, only backup the files that changed on that day. This is can be a problem if you have made changes to files on several different days and need to load each time. This can be very time consuming.

What this basically says it that you need to make some kind of decision about what kind of backup strategy you will use. Also consider that the backup strategy should have backups being done at a time which has the least influence on users, for example in the middle of the night or on weekends.

Details of all this, I actually save for the section on problem solving.

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