Designed to serve a large number of requests and multiple servers,
SANs are sophisticated and complicated hardware devices. A SAN generally includes
??? The SAN itself: Comprised of a huge number of drives, its own internal operating
system, CPUs, and large amounts of RAM, the SAN can present multiple RAID
arrays via separate I/O paths and logical unit numbers (LUNs).
??? Host bus adapters (HBAs): HBAs are special controller cards installed on servers to
enable connectivity to the SAN itself. The type of adapter depends on the connectivity
protocol used. Some connection protocols don??™t require a special piece of
hardware but, rather, a software driver to enable communication over an existing
network.
??? Some sort of HBA switch: This is where the network in storage area network
becomes apparent. NAS devices are simply plugged into existing network switches;
SANs usually have their own network and thus require their own switching device.
The switch coupled with an HBA creates a storage-only communication network,
which significantly improves a SAN??™s reliability.
??? A communication protocol: SANs have their own connectivity protocols, and these
can vary widely depending on the vendor of the SAN and the requirements of your
own infrastructure.
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