Category:Shared disk file systems

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Also known as cluster file systems or SAN file systems.

A Shared Disk File System is a Computer File System with one additional characteristic: It can be accessed in read/write mode concurrently by multiple computing devices. Note that this is not an artifact of communication; many external storage devices permit multiple computers concurrent connectivity. But if multiple devices were to attempt concurrent access to a non-shared file system, the file system would rapidly become corrupt.

The issue is that non-shared file systems have no mechanisms for concurrency control. That is, there's nothing which prevents two devices from performing a modification of the same part of the file system at the same time. Conventional file locking is no aid in this, as it operates above the file system level; it can protect files against concurrent access but offers no protection of the file system itself.

A Shared file system extends the file system concept by adding this concurrency control. It provides each device accessing the file system with a consistent and serializable view of the file system, avoiding corruption and [unintended] data loss.