Backup & Recovery

Chapter 15. Backing Up Databases

Performing regular database backups is one of the hardest tasks that lies before today’s system administrator. The primary reason is that databases are infinitely larger and more complex than simple filesystem files. In order to properly back up a database, you first need to:

Understand the internal structure of your database

Understand the available utilities

Have an excellent working relationship between system administrators, storage administrators, and database administrators

Once you’ve accomplished all of that, you need to choose among your various options:

Shut down the database and back up its files “cold.”

Put the database in a mode that allows its files to be backed up live, or “hot.”

Use its built-in tool to back up to disk or tape without a commercial utility.

Buy an agent for a commercial utility that will back it up to its devices.

Almost anyone who reads this list will find at least one of these steps daunting. Many people work with databases that operate 24 hours a day, 7 days a week. They can’t shut them down for hours at a time to back them up. Even if they could, if a database uses raw devices, it can’t be backed up with a filesystem backup utility. Of course, dd would work on Unix, but that would mean doing one thing for filesystems and a different thing for databases. A common theme throughout this book is that different is bad. Every special case is a chance for failure. It’s something else you have to code for, something else you have ...