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SAN Components

Like a local area network (LAN), SANs use software and hardware components to create a fabric of interconnected storage devices and computers. SAN components consist of the following:

• Storage hardware. Disk-based storage (such as Xserve RAID) is the primary storage media in any SAN solution. Many SANs also use a tape-based system for backup. Appropriate storage hardware should offer high-availability features to prevent data loss or downtime in the event of a disk failure, power outage, or other issue.

• Host bus adapter (HBA). An HBA is an adapter (usually a PCI card, such as Apple’s 2GB Fibre Channel PCI card) that’s installed in each node computer in a storage network an is used to connect the node to a Fibre Channel switch.

• Fibre Channel switch. This multiport device provides the interconnections required to connect multiple Fibre Channel storage devices to computer nodes. Today’s SAN solutions use 1Gb or 2Gb (100MB/s or 200MB/s) Fibre Channel, an open standard technology for reliable, high-speed storage interconnectivity

• Fibre Channel cables. Fibre Channel cables physically connect all of the nodes in a storage network. Copper cables are most economical and used for short distances; optical cables can transmit stored data over many kilometers.

• SAN file system. SAN file system software is the key software component required for building a SAN. A SAN file system (such as Xsan) virtualizes multiple physical storage devices into a single volume and makes it visible to all computer nodes in the SAN. A SAN file system uses a controller to manage metadata, or data about the data, to track the physical location of files and provide file locking to prevent multiple users from accidentally writing to the same file at the same time.

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