New methods of installing storage to servers are constantly created by SAN’s. Such methods improve both the Availability and performance. Nowadays SAN’s are generally used to connect storage arrays that are shared and tape libraries to generally more than one server. SAN’s can also be used for fail-over clustering.
SAN’s are very useful in regards of providing resistance to traditional network bottlenecks as it operates at high speed data transfers between storage devices and servers. There are three possible ways in which data is transferred:
• Server Server: Used for fast, large-volume communications between servers
• Server Storage: This is the default with storage devices. The advantage is that the same storage device may be accessed serially or concurrently by multiple servers.
• Storage Storage: Enables data to be moved without server intervention, thereby freeing up server processor cycles for other activities like application processing. Examples include a disk device backing up its data, to a tape device without server intervention, or remote device mirroring across the SAN.
One of the advantages of SAN is that it allows apps that move data to perform
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Fibre Channels allow the use of SCSI protocols. When SCSI devices are connected they form a bus that can be terminated using something that is called a terminator. The cable length is limited to 25 meters, and allows a 16 device maximum that can be connected to a single SCSI bus. The SCSI protocol has many options that can be configured to handle errors and supports both reconnect and disconnect to various devices and can allow multiple initiator requests. A host computer is generally an initiator. Initiator support allows hosts to attach to the same devices and are used in compatibility of clustered configurations. The ‘Ultra3 SCSI adapter’ has a data transfer rate of 160