World Library  
Flag as Inappropriate
Email this Article

Single-instance storage

Article Id: WHEBN0008609174
Reproduction Date:

Title: Single-instance storage  
Author: World Heritage Encyclopedia
Language: English
Subject: Quantum Corporation, Record linkage, Sis, Windows Home Server
Publisher: World Heritage Encyclopedia

Single-instance storage

Single-instance storage is a system's ability to keep one copy of content that multiple users or computers share. 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 solutions.

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 whilst 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 server solutions 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 a backup solution, single instance storage can reduce the quantity of archive media required since it avoids storing duplicate copies of the same file. Often identical files are installed on multiple computers, for example operating system files. With solutions that use single instance storage, only one copy of a file is written to the backup media therefore reducing space. This becomes more important when the storage is offsite and on cloud such as Storage as a Service like Amazon S3. In such cases, it has been reported that deduplication can help reduce the costs of storage, costs of bandwidth and backup windows by up to 10:1.[1]

Novell GroupWise was built on single-instance storage which accounts for the large data stores that GroupWise is able to achieve.

ISO CD/DVD image files can be optimized to use SIS to reduce the size of a CD/DVD compilation (if there are enough duplicated files) to make it fit into smaller media.

SIS is related to system wide file duplication search and multiple file instance detection tools such as the P2P application Bearshare (5.n Versions and below) but differs in that SIS reduces storage utilization automatically and creates and retains symbolic linkages, whereas Bearshare allows for manual deletion of duplicates and associated user level file system, Windows Explorer type of icon links.


In the United States, Microsoft has a patent related to Single Instance Storage.[2]

Single Instance Storage (SIS) was introduced with the Remote Installation Services feature of Windows 2000 Server. A typical server might hold ten or more unique installation configurations (perhaps with different drivers or software suites) but perhaps only 20% of the data may be unique between configurations.[3] Microsoft states that "SIS works by searching a hard disk volume to identify duplicate files. When SIS finds identical files, it saves one copy of the file to a central repository, called the SIS Common Store, and replaces other copies with pointers to the stored versions."[4] Files are compared solely by their hashes; files with different names or dates can be consolidated so long as the data itself is identical.[3] Windows Server 2003 Standard Edition has SIS capabilities but is limited to OEM OS system installs.

The file-based Windows Imaging Format introduced in Windows Vista also supports single-instance storage. Single-instance storage has been a feature of Microsoft Exchange Server since version 4.0 and is also present in Microsoft's Windows Home Server. It is deduplicating attachments only in Exchange 2007 and was dropped completely in Microsoft Exchange Server 2010.[5] It is protected by several patent applications, including United States Patent numbers 6389433 and 6477544.

Microsoft announced Windows Storage Server 2008 (WSS2008)[6] with Single Instance Storage on June 1, 2009, and states this feature is not available on Windows Server 2008.[6]

See also


This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.