Incremental Backups
By: Staff
Date: October 10, 2006
Level: Intermediate |
By reducing the backup to only the files that have changed, the tape capacity can be significantly reduced. The tape backup program examines the attributes of the files on the hard drive to determine whether they have changed. If they have changed, they are backed up.
An effective backup strategy is to perform a full backup once a week or once a month. In between the full backups, simply back up any files that have changed.
Note: Microsoft recommends that you create a 300-500MB boot and system volume so that you can easily recover from a Registry or disk-drive disaster. By having that volume and booting to a DOS-based operating system, the Registry files are no longer locked and can be copied without limitation. Applications and data files can be put on an NTFS volume using RAID 5 (striping with parity), ensuring their availability (even in the case of a disk-drive failure).
The only problem with this is that FAT volumes offer none of the protection or fault tolerance offered by NTFS volumes. In essence, you must choose between easy copying and restoration versus fault tolerance and security. One solution to this dilemma is to use hardware RAID instead of the software RAID included in Windows NT. Then, you would get optimum protection and still have the ability to boot to DOS and copy or restore the Registry easily.
The disadvantage of an incremental backup strategy is in its restoration after a crash. The restoration process requires that you go back to the full backup and restore it, then restore every incremental backup in order (without skipping any). Skipping is dangerous because the skipped backup may contain a file that was never changed (and hence, was never backed up) on any of the other tapes.
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