A SAN is a dedicated storage network that provides block level access to LUNs. A LUN, or logical unit number, is a virtual disk provided by the SAN. The system administrator the same access and rights to the LUN as if it were a disk directly attached to it. The administrator can partition, and format the disk in any means he or she chooses.
Two networking protocols commonly used in a SAN are fibre channel and iSCSI . A fibre channel network is very fast and is not burdened by the other network traffic in a company's LAN. However, it's very expensive. Fibre channel cards cost around $1000.00 USD each. They also require special fibre channel switches.
iSCSI is a newer technology that sends SCSI commands over a TCP/IP network. While this method may not be as fast as a Fibre Channel network, it does save money by using less expensive network hardware.
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