Synonyms
Shared-disk file system
Definition
The term SAN file system refers to a file system which transfers file data directly to/from a storage device through a SAN. A SAN file system often has the capability of coherency control such that multiple servers may share the file system volume and simultaneously access files stored in the volume. The term shared disk file system is also used to refer to a SAN file system.
Key Points
In contrast to local file systems, SAN file systems allow multiple servers to share file system volumes directly and to access the same file simultaneously. To achieve this, the SAN file system has the capability of coherency control between servers. File system software running on each server may cache file data in a main memory buffer. Suppose that two servers, A and B, have cached the same file X. If A and B were to update X independently at the same time, two versions of X might be generated. The SAN file system needs to let each server be aware of the other servers. When server A updates a fragment of the file X, server B must be informed of a message of cache invalidation or changed information regarding the file X. Some SAN file systems exchange mutual exclusion messages to synchronize write accesses between servers.
The beneficial property of SAN file systems is high performance in comparison with network file systems such as NFS and CIFS. SAN file systems can directly transfer file data between servers and storage devices e.g., on a high-speed Fibre Channel network. In addition, SAN file systems do not need a central file server, which often becomes a bottleneck.
A variety of SAN file systems have been proposed and some of them have been deployed mainly into cluster computer systems often used to run scientific calculations. Recently, SAN file systems are also used as back-end file systems for large-scale enterprise NAS systems.
Cross-References
Recommended Reading
Barrios M, Jones T, Kinnane S, Landzettel M, Al-Safran S, Stevens J, Stone C, Thomas C, Troppens U. Sizing and tuning GPFS. IBM Redbook. SG24-5610-00, 1999.
Burns RC, Rees RM, Long DDE. Semi-preemptible locks for a distributed file system. In: Proceedings of the 19th IEEE International Performance, Computing and Communications Conference; 2000. p. 397–404.
Soltis SR, Ruwart TM, O’Keefe MT. The global file system. In: Proceedings of the 15th NASA Goddard Conference on Mass Storage Systems; 1996. p. 319–42.
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Goda, K. (2018). SAN File System. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_1473
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DOI: https://doi.org/10.1007/978-1-4614-8265-9_1473
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