Understanding the Basic Backup Types

There are many methods for backing up data. The methods used are based on factors such as how convenient the backup or recovery process is or the type of data to be backed up.

Online and Offline Backups

Whereas online backups are performed when Exchange services are still running, offline backups are performed when Exchange services are stopped. With online backups and offline backups, Exchange configuration and user data, system state, and file folders containing Windows and Exchange files can be archived. Typically, online backups are preferred because no interruption to Exchange services is encountered.

Backup Types

Administrators can perform basic types of backups with Exchange 2003:

• Full/Normal backups All selected Exchange data is archived, including data stores and the current transaction logs. This backup type informs Exchange that a full backup has been performed and to clear out the transaction log files.

• Copy backups All selected Exchange data is archived, including data stores and the current transaction logs. This backup type does not inform Exchange that a full backup has been performed and to clear out the transaction logs. This allows other backup types to be completed later on.

• Differential backups Creates backup copies of all data changed since the last normal backup. The actual data stores are not backed up, only the transaction logs are backed up, and the log files are not cleared. Recovering Exchange involves applying the current full backup and then the most recent differential backup.

• Incremental backups Creates backups of data that has changed since the last normal or incremental backup. The actual data stores are not backed up, only the transaction logs are backed up, and the log files are cleared after the incremental backup is completed. Recovering Exchange involves applying the current full backup and then applying each incremental backup after the full backup.

A typical backup plan will include performing full backups on a weekly basis and supplementing them daily with incremental or differential backups. Be sure to store a backup set offsite in case of an unexpected disaster.

Caution

The type of backup depends on the configuration of circular logging. Administrators can specify circular logging settings at the Exchange Storage Group level. Differential or Incremental backups cannot be used if circular logging is enabled. Circular logging allows Exchange to overwrite log files, which prevents reliable restores from the transaction logs.