SAN and NAS defined
Summary
Topics
A SAN (see Figure 1) is a high-speed subnetwork of devices that lets you offload traffic from your main network. Usually composed of RAID arrays connected via Fibre Channel, a SAN communicates with servers and clients through SCSI commands instead of TCP/IP, handling data at the block level. A NAS (see Figure 2) is typically composed of networked file servers that make use of Ethernet and TCP/IP, handling data at the file level. You attach NAS devices to an existing TCP/IP network (usually Ethernet) to add additional storage.
A simple way to remember the difference between SAN and NAS is to think about how each technology is implemented. NAS is commonly found in server farms--application servers, e-mail servers, and so on--where increasing storage volume is as easy as attaching another system to the network. A SAN is usually deployed for e-commerce applications, data backup and other cases in which large amounts of data must be stored and transmitted over a network; a SAN lets you offload such high-volume traffic, sparing your Ethernet network from congestion.
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