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Post-processing deduplication (PPD), also known as asynchronous de-duplication, is the analysis and removal of redundant data after a backup is complete and data has been written to storage. PPD can be contrasted with inline deduplication, a process in which redundant data is identified and referenced (instead of copied) while the backup is being written.
Both methods have their own advantages and disadvantages. One advantage of PPD is that because the backup is straightforward, it takes less time. A disadvantage of PPD, however, is that the storage administrator must have enough space to store the full backup somewhere until the duplicate data is removed.