Postdeduplication

Postdeduplication refers to the process of identifying and removing redundant data after it has already been stored. This is in contrast to in-line deduplication, where data is analyzed and redundant blocks are identified and eliminated before they are written to storage. In postdeduplication, data is initially stored without deduplication, and a separate process runs later to scan the stored data, find identical chunks, and replace subsequent occurrences with pointers to the first instance.

The primary benefit of postdeduplication is that it does not introduce latency during the initial data write operations. This can be crucial for applications that are sensitive to write performance. By deferring the deduplication process, the system can ingest data more rapidly. However, postdeduplication can consume significant system resources during its execution, potentially impacting read performance or requiring scheduled maintenance windows. The storage space savings are realized only after the deduplication process completes.

There are several approaches to implementing postdeduplication. Some systems perform a full scan of all data, while others use metadata or indexing techniques to identify potential duplicates more efficiently. The effectiveness of postdeduplication is dependent on the nature of the data being stored and the algorithms used to identify redundant segments. It is often employed in backup and archiving solutions where read performance is less critical than write throughput during data ingestion.