Network-attached storage (NAS) is file-level "computer data storage connected to a "computer network providing data access to a "heterogeneous group of clients. NAS devices specifically are distinguished from file servers generally in a NAS being a "computer appliance – a specialized computer built from the ground up for serving files – rather than a general purpose computer being used for serving files (possibly with other functions). In discussions of NASs, the term "file server" generally stands for a contrasting term, referring to general purpose computers only.
As of 2010[update] NAS devices are gaining popularity, offering a convenient method for sharing files between multiple computers. Potential benefits of network-attached storage, compared to non-dedicated file servers, include faster data access, easier administration, and simple configuration.
NAS systems are networked "appliances containing one or more hard drives, often arranged into logical, redundant storage containers or "RAID arrays. Network Attached Storage removes the responsibility of file serving from other servers on the network. They typically provide access to files using network file sharing protocols such as "NFS, SMB/CIFS ("Server Message Block/Common Internet File System), or "AFP.
File servers generally offer some form of system security to limit access to files to specific users or groups. In large organizations, this is a task usually delegated to what is known as "directory services such as "openLDAP, Novell's "eDirectory or Microsoft's "Active Directory.
These servers work within the hierarchical computing environment which treat users, computers, applications and files as distinct but related entities on the network and grant access based on user or group credentials. In many cases, the directory service spans many file servers, potentially hundreds for large organizations. In the past, and in smaller organizations, authentication could take place directly at the server itself.