NAS

Network-attached storage (NAS) is a file-level computer data storage connected to a computer network providing data access to heterogeneous network clients.

Information Technology (IT) departments are looking for cost-effective storage solutions that can offer performance, scalability, and reliability. As users on the network increase and the amounts of data generated multiply, the need for an optimized storage solution becomes essential. Network Attached Storage (NAS) is becoming a critical technology in this environment.

The benefit of NAS over the older Direct Attached Storage (DAS) technology is that it separates servers and storage, resulting in reduced costs and easier implementation. As the name implies, NAS attaches directly to the LAN, providing direct access to the file system and disk storage. Unlike DAS, the application layer no longer resides on the NAS platform, but on the client itself. This frees the NAS processor from functions that would ultimately slow down its ability to provide fast responses to data requests.

In addition, this architecture gives NAS the ability to service both Network File System (NFS) and Common Internet File System (CIFS) clients. As shown in the figure below, this allows the IT manager to provide a single shared storage solution that can simultaneously support both Windows*-and UNIX*-based clients and servers. In fact, a NAS system equipped with the right file system software can support clients based on any operating system.

NAS is typically implemented as a network appliance, requiring a small form factor (both real estate and height) as well as ease of use. NAS is a solution that meets the ever-demanding needs of today s networked storage market.

A NAS unit is essentially a self-contained computer connected to a network, with the sole purpose of suppling file-based data storage services to other devices on the network. The operating system and other software on the NAS unit provide the functionality of data storage, file systems, and access to files, and the management of these functionalities. The unit is not designed to carry out general-purpose computing tasks, although it may technically be possible to run other software on it. NAS units usually do not have a keyboard or display, and are controlled and configured over the network, often by connecting a browser program to their network address.

The alternative to NAS storage on a network is to use a computer as a file server. In its most basic form a dedicated file server is no more than a NAS unit with keyboard and display and an operating system which, while optimised for providing storage services, can run other tasks; however, file servers are increasingly used to supply other functionality, such as supplying database services, email services, and so on.

A general-purpose operating system is not needed on a NAS device, and often minimal-functionality or stripped-down operating systems are used. For example FreeNAS, which is open source NAS software designed for use on standard computer hardware, is just a version of FreeBSD with all functionality not related to data storage stripped out. NASLite as the name suggests is a highly optimized version of Linux running from a floppy disk for the sole purpose of a NAS, Likewise, NexentaStor is based upon the core of the NexentaOS, an open source hybrid operating system with an OpenSolaris core and a Linux user environment.

NAS systems contain one or more hard disks, often arranged into logical, redundant storage containers or redundant RAID arrays (redundant arrays of inexpesive/independent disks). NAS removes the responsibility of file serving from other servers on the network.

NAS uses file-based protocols such as NFS (popular on UNIX systems) or SMB (Server Message Block) (used with MS Windows systems). NAS units rarely limit clients to a single protocol.