What Is a SCSI and RAID Hard Drive?
SCSI-based hard drives were developed to replace older and slower IDE hard drives, but they tend to be more expensive. A RAID is technically not a hard drive but rather a way of arranging and managing a set of independently running hard drives on one computer system; the drives can be either SCSI-based or IDE-based. A RAID has an advantage over single hard drives in terms of performance, data recovery and reliability, but recent research has shown that an IDE-based RAID can be both less expensive and faster than SCSI-based RAIDs.
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SCSI Hard Drive
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SCSI, usually pronounced "scuzzy," is short for "Small Computer System Interface," and it is a set of industry standards that guides the development and engineering of peripheral devices (e.g., hard drives, zip drives, printers) for use with a SCSI bus. What sets SCSI apart from other data transfer standards is that it is based on parallel data transfer rather than serial data transfer. A SCSI hard drive is a hard drive designed to interface with a SCSI bus.
RAID
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RAID is short for "Redundant Array of Independent Disks." It is not a hard drive in and of itself. Rather, it is a way of coordinating the operations of many independent hard drives in a parallel fashion. RAID is a way to increase the amount of hard drive space available to a computer system. The RAID, collectively, is more reliable than any one of its single hard drives because the RAID can use the resources of one hard drive to offset any errors in another hard drive. For example, it can keep redundant data on one drive in case of failure of another drive. A RAID can hold and manage a collection of both SCSI-based hard drives and non-SCSI-based hard drives. The most common non-SCSI hard drive is the IDE hard drive, an older type of hard drive that is still widely used.
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SCSI RAID verses Non-SCSI RAID
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A group of researchers from the University of Virginia and Bell Laboratories has challenged the idea that an IDE-based RAID is at a disadvantage compared with a SCSI-based RAID in terms of reliability and performance. They found that in the case of random I/O, a SCSI-based RAID is faster than an IDE-based RAID, but the IDE-based RAID can be significantly improved by using I/O scheduling in the kernel, soft updates and journaling. They conclude that IDE-based RAIDs can be both less expensive and faster than SCSI-based RAIDs.
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