[ The PC Guide | Systems and Components Reference Guide | Hard Disk Drives | Hard Disk Performance, Quality and Reliability | Redundant Arrays of Inexpensive Disks (RAID) | Why Use RAID? Benefits and Costs, Tradeoffs and Limitations ]

The many benefits of RAID do not come without some costs. (This is self-evident simply by the fact that most PCs do not use RAID arrays.) Most of the attention when it comes to RAID costs is paid to the hardware, but there are other costs that can dwarf the dollars (pounds, lira, shekels) paid for hardware. It's impossible to say exactly what a RAID implementation will cost because they can vary from simple setups costing only a couple of hundred dollars, to enormous arrays that cost as much as a small house.

When considering if RAID is right for you, don't forget to add in the costs in all of these major categories, where relevant:

• Planning and Design: For a decent-sized RAID system, you must allow some resources for planning what type of RAID will be implemented, deciding on array size, choosing hardware, and so on.
• Hardware: Hardware costs include hard disks, enclosures, power supplies, power protection and possibly a hardware RAID controller. While "high-end" RAID requires all of the above, "economy" RAID implementations can be done within a regular PC case, using the existing PC power supply and protection, and either an inexpensive hardware controller or no controller. Most people think immediately of the cost of the hard disks in a RAID system when they think about expenses associated with RAID. This is only true to a point, and it depends on what RAID level is being implemented. Remember that if you need "X" amount of space for your files, you're going to have to buy "X" worth of hard disks regardless. RAID only costs extra in this regard to the extent that additional drives must be purchased for redundancy. If you are implementing RAID 0, there is no additional disk drive cost unless you are buying extra-large drives and you don't really need the full capacity of the array.
• Software: Most hardware RAID solutions come with all the software you need to operate them. If you are doing software RAID however, you need an operating system such as Windows NT or Windows 2000 that provides this functionality. Of course, you may already be planning to use an operating system with software RAID support anyway...
• Setup and Training: Simple RAID systems in individual PCs don't really require training, and are easy to set up. Larger RAID systems can require many hours to set up and configure, and training of IS professionals may be required.
• Maintenance: Enterprise-class RAID systems require ongoing maintenance if they are to continue to provide the organization with high availability and performance.

Obviously, the costs are highest for businesses implementing large arrays. For these companies, however, these costs must be compared to the costs of data loss, data recovery and interruption of availability that would result if RAID were not used. For many companies, the entire cost of a RAID setup pays for itself the first time it prevents their enterprise system from having to be taken down for half a day to deal with a hardware failure.

Next: RAID Tradeoffs

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