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Backup and recovery enhancements in SQL Server 2005

The backup and restore capabilities of SQL Server 2005 are largely unchanged from SQL Server 2000, but there are several new features worthy of your attention. Edgewood Solutions' Greg Robidoux explains the pros and cons of using these features -- from mirrored backups to online restores.

As with any new software release, you'll often find new features you didn't know existed or you didn't know you needed. Many backup and restore features that exist in SQL Server 2000 will remain the same in SQL Server 2005, but there are several new enhancements worth your consideration.

Mirrored backups

SQL Server 2005 lets you create mirrored backups. A mirrored backup allows you to create two or four identical copies of the backup files in case one of the sets is damaged. The mirrors have identical contents, so you can mix the files in the event that one becomes corrupt.

Say you have mirror set 1 and mirror set 2, both with full backups and transaction log backups. If the full backup for mirror set 1 becomes corrupt, you can do a restore using the full backup from mirror set 2 and then continue using the transaction log backups from mirror set 1.

Online restores

You also have the ability to do an online restore, but, don't get too excited. From the name, it sounds like you can keep the entire database up and running and have users in the database when you do a restore -- but that is not the case. Online restores allow you to restore an offline filegroup while keeping the database online. So you can keep most of your database up and running, but the filegroup you want to restore has to be offline.

Note: To run this feature, you must be using SQL Server 2005 Enterprise Edition, and the primary filegroup cannot be offline. Plus, you have to make sure your application can take filegroups offline and still be able to function. With careful planning this could be very useful, but it will probably not be a feature many people will use.

Copy only backups

A feature I think will get a lot of mileage is copy only backups, which gives you the ability to make a copy in the middle of your backup sequence without disrupting the sequencing of the other backup files. Using SQL Server 2000, if you run a special full backup in the middle of the day, in order to restore, you must use that full backup and any transaction log that occurred after that full backup. This new feature allows you to create a copy only backup and then use your normal full backup for recovery purposes.

For differential backups, there is no change in the way the process works. For transaction log backups, you also have the ability to do copy only backups -- again without disrupting the sequencing of the other backup files. Any backup created using this option is marked as copy_only in the backup tables.

Partial backups

You may think partial backups are the same as differential backups -- but they are not. A partial backup backs up all filegroups except those filegroups marked read only, unless specified. For a read-only database, only the primary filegroup is backed up. If you have a lot of static data in read-only filegroups, this could be a much faster way to back up your database.

Restore from previous versions

One thing that remains the same in SQL Server 2005 is the ability to restore databases from earlier versions; you can restore database backups from SQL 7.0 and 2000. (There is, however, still no way to restore backups from 6.5.)

Note: You have not been able to restore system databases from prior versions, and the same holds true in SQL Server 2005.

I've highlighted several new backup and restore features to investigate with SQL Server 2005. The SQL Server 2005 September CTP is the latest version. Download a copy and begin learning about these new features and how you can take advantage of them when SQL Server 2005 is released in November.

About the author: Greg Robidoux is the president and founder of Edgewood Solutions LLC, a technology services company delivering professional services and product solutions for Microsoft SQL Server. He has authored numerous articles and has delivered presentations at regional SQL Server users' groups and national SQL Server events. Robidoux, who also serves as the Backup and Recovery expert, welcomes your questions.

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