Embedded Agents

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Synthetic Backups

Synthetic backups will offer the technology to allow less frequent full and cumulative incremental backups while still allowing acceptable restore performance. Generally speaking, you establish the frequency for full backups based on recovery requirements and volatility of data. The less frequently you do full backups, the more images will be required to do a full filesystem or volume recovery. Synthetic backups will create new (synthetic) full backups from a series of incremental backups and new (synthetic) cumulative incremental backups from a series of differential incremental backups. The intent is that you will be able to schedule synthetic backups just like normal ones.

The basic idea behind synthetic backups is to manufacture a compact set of data from a disparate set of data spread among many pieces of removable media. It is essentially a restore operation used to manufacture a new full backup. The first task in creating a synthetic backup is to determine the data that needs to be collected to manufacture your new image. For a synthetic full backup, the last full backup is used as a reference point for collecting this data. For a synthetic cumulative backup, the backup sets or images are peers of each other and can span any time period between the last full backup and the current date.

The next task is to look into the catalog entries for the constituent backup sets or images and determine which files are necessary for the final new synthetic image. Basically, the most recent unique sets of objects are the ones desired for the synthetic backup. The time of the backup is used to order the objects correctly. Based on this information, the selected data is routed to a destination media that will constitute a synthetic backup. At the conclusion of the operation, the files now need to be appropriately cataloged as either a new full or cumulative incremental backup. You would now have a viable new compact set of media that represents a point in time of your data as recent as your latest offline copy.

Once again, disk-based backup solutions will add tremendous value when creating these synthetic full backups to tape; its random access serves quite well in this scenario.

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