Computer-Teacher

Author: arun

Windows XP Backup provides five backup types that define what data is backed up, such as only files that have changed since the last backup.
Some backup types use backup markers, also known as archive attributes, which mark a file as having changed. When a file changes, an attribute is set on the file that indicates that the file has changed since the last backup. When you back up the file, this clears or resets the attribute.

Normal

During a normal backup, all selected files and folders are backed up. A normal backup does not rely on markers to determine which files to back up. During a normal backup any existing marks are cleared and each file is marked as having been backed up. Normal backups speed up the restore process because the backup files are the most current and you do not need to restore multiple backup jobs.

Copy

During a copy back?up, all selected files and folders are backed up. It neither looks for nor clears markers. If you do not want to clear markers and affect other backup types, use copy. For example, use a copy backup between a normal and an incremental backup to create an archival snapshot of network data.

Differential

During a differential backup, only selected files and folders that have a marker are backed up. It does not clear markers. Because a differential backup does not clear markers, if you did two differential backups in a row on a file and nothing changed in the file, the entire file would be backed up each time.

Incremental

During an incremental backup, only selected files and folders that have a marker are backed up. It clears markers. Because an incremental backup clears markers, if you did two incremental backups in a row on a File and nothing changed in the file, the file would not be backed up the second time.

Daily

During a daily backup, all selected files and folders that have changed during the day are backed up. It neither looks for nor clears markers. If you want to back up all files and folders that change during the day, use a daily backup.

Combining Backup Types

An effective backup strategy is likely to combine different backup types. Some backup types require more time to back up data but less time to restore data. Conversely, other backup types require less time to back up data but more time, to restore data. If you combine backup types, markers are critical. Incremental and differential back?up types check for and rely on the markers. The following are some examples of combining different backup types:

Normal and differential backups. On Monday a normal backup is performed and on Tuesday through Friday differential backups are performed, Differential backups do not clear markers, which means that each backup includes all changes since Monday. If data becomes corrupt on Friday, you only need to restore the normal backup from Monday and the differential backup from Thursday This strategy takes more time to back up but less time to restore.

Normal and incremental backups. On Monday a normal backup is performed and on Tuesday through Friday incremental backups are performed. Incremental backups clear markers, which means that each back?up includes only the files that changed since the previous backup. If data becomes corrupt on Friday, you need to restore the normal back?up from Monday and all incremental backups, from Tuesday through Friday. This strategy takes less time to back up but more time to restore.

Normal, differential, and copy backups. This strategy is the same as the first example that used normal and incremental backups except that on Wednesday you perform a copy backup. Copy backups include all selected files and do not clear markers or interrupt the usual backup schedule. Therefore, each differential backup includes all changes since Monday. The copy backup type done on Wednesday is not part of the Friday restore. Copy backups are helpful when you need to create a snapshot of your data.

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