Is SIS (Single Instance Store) a form of deduplication?
Reducing duplicate file copies is a limited form of deduplication sometimes called single instance storage or SIS. This file level deduplication is intended to eliminate redundant (duplicate) files on a storage system by saving only a single instance of data or a file. If you change the title of a 2 MB Microsoft Word document, SIS would retain the first copy of the Word document and store the entire copy of the modified document. Any change to a file requires the entire changed file be stored. Frequently changed files would not benefit from SIS. Data deduplication, which reduces sub-file level data, would recognize that only the title had changed – and in effect only store the new title, with pointers to the rest of the document’s content segments. Generally, Data Domain enables 2x-4x data reduction on an initial full backup, 6x-7x reduction on subsequent file-level incrementals, and 50x-60x reduction on subsequent full backups. SIS does not offer benefit to the initial full or to file
