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 320-2 – Host-Based RAID Solution

RAID products are either host-based or external.

The MegaRAID SCSI 320-2 controller is a host-based RAID solution. The MegaRAID SCSI 320-2 is a PCI adapter card that is installed in any available PCI expansion slot in a host system.

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 320-2 is part of the file server, so it can transmit data directly across the computer’s buses at data transfer speeds up to 532 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 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.

2-2

Introduction to RAID

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