Nearline storage
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Nearline storage (where the word "nearline" is a contraction of near-online) is a term used in computer science to describe an intermediate type of data storage that represents a compromise between online storage (supporting frequent, very rapid access to data) and offline storage/archiving (used for backups or long-term storage, with infrequent access to data)[1][2]. The nearline storage system knows on which volume (cartridge) the data resides, and usually asks a robot to retrieve it from this physical location (usually: a tape library) and put it into a tape drive to enable access by bringing the data it contains online[3]. This process is not instantaneous, but it only requires a few seconds.
Both archiving and nearline allow a reduction of database size that results in improved speed of performance for the online system. However, accessing archived data is more complex and/or slower than is the case with nearline storage, and can also negatively affect the performance of the main database, particularly when the archive data must be reloaded into that database[4].
The term NEARLINE, in stylized form or as a typed drawing, is a registered word mark (trademark) of the Storage Technology Corp (now StorageTek, acquired by Sun Microsystems in 2005).
The term "nearware" is now being used to describe the equipment used for nearline" storage. As with "firmware", "middleware", and "shareware", the suffix '-ware' has been adopted by the storage community to designate the general product range associated with Nearline storage.
The term "Nearline 2.0" has been used by software manufacturer SAND Technology to refer to a software-based nearline data repository employing standard disk storage devices. In Nearline 2.0, data compression allows considerably more data to be stored in a given amount of disk space than is the case with other formats; this data can be searched and retrieved without first being decompressed, meaning that less data needs to be read from disk to access a desired piece of information. This results in a significant increase in the speed of data operations compared with earlier nearline methods. This type of nearline storage is a central component of SAP's Information Lifecycle Management (ILM) architecture, designed to optimize performance and reduce disk costs for the main database of the SAP BI system.
[edit] References
- ^ "Nearline storage" in "A Glossary of Archival and Records Terminology". Retrieved on 2009-01-30.
- ^ Venkatramani, Chitra and Tzi-cker Chiueh (1993). "Survey of Near-Line Storage Technologies: Devices and Systems". Experimental Computer Systems Laboratory.
- ^ "Near-line storage" in "Webopedia Computer Dictionary". Retrieved on 2009-01-30.
- ^ Ritchie, Arthur (2008), "Nearline and archiving in the data warehouse: what's the difference?". Database and Network Journal, October issue. Retrieved on 2009-01-30.
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