Backup and disaster recovery are critical elements of data management. Back up and disaster recovery of file systems means copying file systems to removable media, such as tape, to safeguard against loss, damage, or corruption and then copying current backup files from removable media to a working directory. If a system crash causes loss of data that is in its memory or if software or hardware failure causes corruption in the contents of a database, you may need to recover data. Software or hardware failure can require a restore from backup.
You can repair damage from a system crash by performing a “soft recovery” when you restart the server. A soft recovery is a process that runs automatically when you try to start the information store after a system failure. Soft recovery uses the log files and database files on the disk instead of using tape backup. If your server crashes and the contents of memory are lost, the database file on disk is flagged as inconsistent.
If soft recovery does not work or if there is a more serious problem within the system, you need to restore from backup. The process for restoring from an online backup is similar to soft recovery. Exchange Server makes sure that all of the files are put in the right place and brings the database up to a consistent state. When you restore data from tape backup, the restore process returns to disk all of the files that were backed up.
The most time-consuming aspect of doing a restore is not copying the database files back to the disk but replaying the log files. It may take several hours to replay log files on large servers during a restore.
Sometimes users delete some messages but later realize that they should not have deleted them. It cannot easily restore individual messages in a mailbox from backup. However, there is a way for users to recover messages that they have deleted from a mailbox without having to resort to backups. The Recover Deleted Items feature that comes with Exchange Server 5.5 lets a user retrieve messages from the Deleted Items folder in Outlook if you enable the feature on the server.
Proper back up and better management of disasters can make your data much safer. Regular backups are critical, preferably every night and monitor your backups, track the status of the database engine and the information store, and do not ignore error messages. Decide how big you will allow your information store to grow, and manage it at that level. Test and practice your backup and disaster management procedures.