A SAN is made up of three major component areas:
Fibre channel infrastructure technology that creates the SAN fabric Storage systems on which data is stored and protected Storage and SAN management software that delivers unified, automated management throughout the SAN.
A storage area network, in its purest sense, is a separate computer network, typically based on a 'fabric' of fibre channel, switches and hubs that connects storage devices to a heterogeneous set of servers on a many-to-many basis.
A SAN can also enable direct storage-to-storage interconnectivity, and lends itself to exploiting new breeds of clustering technology. It also helps get the best out of Network Attached Storage(NAS) devices that can intelligently provide disk and tape capabilities to one or more servers.
SANs use fibre technology as a medium over which data is sent at very high speeds and bandwidths across great distances. SAN-enabled devices, e.g. disks, servers, tape libraries, etc. can then connected onto the SAN through sophisticated fibre hubs/switches, which can be configured with multiple links to allow fault tolerance and load balancing.
The solution can be configured in a highly scalable manner, providing connectivity to hundreds of servers and vast amounts of storage capacity.
Users connect via a Local Area Network (LAN) and/or Wide Area Network (WAN) through the application servers into the data.
In effect, the application server is simply acting as an access path into the data.
This is a new way of looking at your business-computing environment. What's more, if suitable architecture exists, compatible spare server capacity can take over the user processing needs if the application server fails.
This new storage topology facilitates a new architecture for enhancing availability, and leads us to the interesting notion that application servers in a SAN-aware cluster can be considered as 'application server peripherals' around the users' data. It also shows that the typical 'failover' high availability solution of today that requires 100% redundant hardware can be replaced by one where, say, a 32-machine cluster can enable each server to provide 'application takeover' facilities for its peers. This provides equal or better availability with far less hardware.
With additional hardware and software, multiple paths from the server to the storage array can be configured to allow no single point of failure (NSPOF) to give constant access to data.
Disks within the storage arrays can be configured in a multitude of ways; Grouped to provide RAID configurations e.g. striped, striped with parity, mirrored etc
Snapshot disks (which take a picture of a pre-selected disk/s) Online spares (which automatically take over in the event of a disk failure) This level of redundancy can then be complemented by other fault-tolerant solutions such as NIC teaming and clustering servers to give complete application redundancy.
