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Delta Indexes for Incremental Backups


Advantages of Full indexes:

Incrementals are self describingNo additional backup files are required to be loaded other than the most recent Incremental when appending to an existing backup set. This enables backup sets to be 'split' over multiple locations; useful if you want to archive part of a backup set.
Mounting incremental backups is fastBecause the entire index is available when the Incremental file is opened the backup set can be mounted and browsed in Windows Explorer very quickly.
See: Browsing Macrium Reflect images and backups in Windows Explorer 

Disadvantages of Full indexes:

Increases the size of Incremental backupsWhen running Incremental backups on a data set where very little has changed the overhead of the Full index may be greater than the size of the data that's backed up.
Consolidation causes subsequent Incrementals to be updatedIf your backup 'Retention Rules' invoke a 'Synthetic Full' or 'Incremental Merge' then indexes contained in more recent Incrementals are updated to reflect the consolidation. Without updating the Index would become 'stale'. This file change can cause excessive file copying when synchronizing consolidated backup sets to an archive location. See: Backup Folder Synchronization for more information on this.


Advantages of Delta indexes

Decreases the size of Incremental backupsThe Incremental file index contains only a list of the changed data blocks in the incremental. This means that Incremental backups with only a few changes are optimized for backup file size. This is most apparent when performing frequent Incremental backups.
Later Incrementals are unaffected by ConsolidationBecause the Incremental index only contains references to itself there is no need to update the Incremental backup file when earlier backups in the same set are consolidated. This overcomes the issue with Backup Folder Synchronization  caused by Full indexes.

Disadvantages of Delta Incremental

Incrementals depend on all previous backupsA backup set cannot be appended to unless all previous files in the set are available in the same folder as the most recent Incremental. Partial archiving of a backup set is not possible.
Mounting incremental backups may be slowerBecause the Full Index has to be constructed when the Incremental file is opened, this can lead to a delay of a few seconds when browsing images and backups in Windows Explorer.



Enable Changed Block Tracker for Incremental Backups

For information on CBT please see here



Note: A backup set can contain a mixture of Incremental backups with Full and Delta Indexes. If Delta Indexing is enabled mid backup set, then only Incrementals created after enabling will contain delta indexes.

Please ensure that you are using Rescue Media created with Macrium Reflect v6.1 if Delta Indexing is enabled. 
Click the 'Rebuild' button on the final Rescue Media Wizard page. See:  Creating rescue media for more information.

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