2.1.2Increased Reliability

The electromechanical components of a disk subsystem operate more slowly, require more power, and generate more noise and vibration than electronic devices. These factors reduce the reliability of data stored on disks. RAID provides a way to achieve much better fault tolerance and data reliability.

2.2MegaRAID SCSI 320-0 – Host-Based RAID Solution

RAID products are either host-based or external.

The MegaRAID SCSI 320-0 controller is a host-based RAID solution. The MegaRAID SCSI 320-0 is a PCI adapter card that is installed in a PCI expansion slot in a host system with a motherboard that contains the LSI Logic 53C1030 SCSI chip.

2.2.1Host-Based RAID

A host-based RAID product puts all of the RAID intelligence on an adapter card that is installed in a network server. A host-based RAID product provides the best performance. MegaRAID SCSI 320-0 is part of the file server, so it can transmit data directly across the computer’s buses at data transfer speeds up to 132 Mbytes/s.

The available sequential data transfer rate is determined by the following factors:

￿The sustained data transfer rate on the motherboard PCI bus

￿The sustained data transfer rate on the i960RM PCI to PCI bridge

￿The sustained data transfer rate of the SCSI controller

￿The sustained data transfer rate of the SCSI devices

￿The number of SCSI channels

￿The number of SCSI disk drives

Host-based solutions must provide operating system-specific drivers.

2-2Introduction to RAID

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