Single-instance storage
simple type of data deduplication
Single-instance storage (SIS) is a system's ability to take multiple copies of content and replace them by a single shared copy. It is a means to eliminate data duplication and to increase efficiency. SIS is frequently implemented in file systems, e-mail server software, data backup, and other storage-related computer software. Single-instance storage is a simple variant of data deduplication. While data deduplication may work at a segment or sub-block level, single-instance storage works at the whole-file level and eliminates redundant copies of entire files or e-mail messages.
Concept
In the case of an e-mail server, single-instance storage would mean that a single copy of a message is held within its database while individual mailboxes access the content through a reference pointer. However, there is a common misconception that the primary benefit of single-instance storage in mail servers is a reduction in disk space requirements. The truth is that its primary benefit is to greatly enhance delivery efficiency of messages sent to large distribution lists. In a mail server scenario disk space savings from single-instance storage are transient and drop off very quickly over time.
When used in conjunction with backup software, single-instance storage can reduce the quantity of archive media required since it avoids storing duplicate copies of the same file.
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This entry incorporates text from “Single-instance storage” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.