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compared with
Version 4 by David Wartell
on Dec 23, 2008 10:07.

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The Virtual Full Backup method requires that a database be used to store block deltas.  R1Soft calls this a Disk Safe ®  While in theory an SQL type database could be used in pratice they do not deal with large amounts of binary block efficiently so custom tailored data stores are used.  The important function of the block deltas database is to map what versions of blocks are allocated and used by particular recovery points.  This facilitates the efficient retrieval of blocks belonging to a recovery point as well as the process of merging.  Merging involves deleting a recovery point and deltas specific to that recovery point not needed by other recovery points that are not being deleted.
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h4. Merging (Deleting) Recovery Points


The impact of the Virtual Full Backups on performance is as little as possible since only the deltas between synchronizations are read form the live server Disk(s).  And unlike the other methods Deltas are only ever stored one time in the backup storage medium.
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