What is NAS?
NAS is short for Network Attached Storage and is a term applies to an external storage device that attaches to your network hence enables multiple users and computers to store and share their data in a central place.
NAS devices make it convenient for files sharing between numbers of connected clients. Also, compared with file servers, faster data access is enabled, as well as easier administration, more basic and straightforward configuration. It can also act as an external backup device if needed, thus by using a NAS you can easily get extra storage for all your networked computers. From this perspective, NAS can be quite cost effective in the long run.
What is SAN?
SAN stands for storage area network. It is a dedicated network that is separate from LANs (local area networks) and WANs (Wide Area Networks). Generally, it is used to connect all the storage resources that are connected to various servers. It is constituted by a collection of SAN hardware and software. A SAN typically has its own network of storage devices that are generally not accessible through the LAN by other devices. It does not provide file abstraction, only block-level operations. However, file systems which built on top of SANs do provide file-level access, and are known as SAN file systems or shared disk file systems.
The role of SAN
SANs play important role in data backup and disaster recovery settings. Within a SAN, data can be transferred from one storage device to another without interacting with a server. This raises the speed of backup process and you do not need to use server CPU cycles for backup. What's more, Fibre Channel technology or some other networking protocols are used in SANs so as to enable the network to span longer distance geographically. All these make it more feasible for companies to achieve the goal of backing up data in remote locations.
Using a SAN can also simplify some management tasks, allowing organizations to hire fewer IT workers or to free up some of them for other tasks. To boot servers from a SAN is also possible, which can effectively reduce the time and hassles involved in replacing a server.
SAN vs NAS
As is often the case, people may confuse the term SAN with the term NAS. An effective way to distinguish the two is to look out the last term of each acronym: a SAN stands for storage area network and is an actual network, while NAS stands for network-attached storage and refers to a storage device, typically in an IP network. Differ from SANs that provide block-level storage for servers, a NAS device offers file-level storage for end users. Operating systems see a SAN as a disk, while they regard a NAS device as a file server. Both SAN and NAS provide networked storage solutions. A NAS is a single storage device that operates on data files, while a SAN is a local network of multiple devices that operate on disk blocks.
The administrator of a home or a small business network can connect a NAS device to his LAN. He can also set up automatic or manual backups between the NAS and all other connected devices. The NAS keeps its own IP address comparable to computer as well as other TCP/IP devices and has a capacity of up to a few terabytes of data. Administrators can install additional NAS devices for more storage capacity to their network, although each NAS operates independently. Administrators of larger enterprise networks may require many terabytes of centralized file storage or very high-speed file transfer operations. In this situation, installing an army of many NAS devices is not a practical option; they can instead turn to a single SAN that contains a high-performance disk array to provide the needed scalability and performance.