File storage, also called file-level or file-based storage, stores data in a hierarchical structure. The data is saved in files and folders, and presented to both the system storing it and the system retrieving it in the same format. Data can be accessed using the Network File System (NFS) protocol for Unix or Linux, or the Server Message Block (SMB) protocol for Microsoft Windows.
NFS, originally developed by Sun Microsystems, allows a client to store and view files on a server as if they were on the client computer. All or part of the file system can be mounted on a server, where it is accessible by clients with assigned privileges to a file. SMB uses data packets sent by a client to a server, which responds to the request. Most network-attached storage (NAS) systems support NFS and SMB, which was formally known as the Common Internet File System.
File vs. block storage
While block-level storage systems write and retrieve data to and from certain blocks, file-level storage requests data through user-level data representation interfaces. This client-server method of communication occurs when the client uses the data's file name, directory location, URL and other information. With block-level storage, the server receives the filing request, looks up the data storage locations where the data is stored and retrieves it using storage-level functions. The server does not send the file to the client as blocks, but as bytes of the file. File-level protocols cannot understand block commands, and block protocols cannot convey file access requests and responses.
Unified storage, also known as multiprotocol storage, offers Fibre Channel and iSCSI block-level access found in storage area network (SAN) systems and NAS file-level access in one box. Unified storage was first used around 2002, and is now a common storage architecture.
Individual NAS and SAN enterprise file storage products may also offer advanced data management features, such as data deduplication and thin provisioning, which can provide greater value with virtual infrastructures.
Growth of file storage systems
In recent years, data center trends, such as big data analytics and cloud storage technologies, have fostered the rapid growth of computer file storage. The number of applications using strictly file-based access, rather than database access, has been another contributing factor.
NAS filers are generally the most effective way to deal with file data growth. But too many filers can lead to isolation, as users may lack a global namespace across the multiple platforms. This causes administrators to run multiple systems simultaneously.
While adding NAS systems is the right approach to dealing with the explosion in computer file storage, the preferred method is to use a scale-out NAS system, clustered NAS system or NAS file virtualization to run them concurrently.
See also: network-attached storage (NAS)