The MAID concept was developed in 2001- 2002 and brings the acquisition price and operating expense of disk storage closer to that of an automated tape library. MAID was the first effective "Green Disk Array" to appear. Five years later, many issues about MAID are not well understood.
For example, with MAID, disks are powered off when not in use yielding considerable energy savings. But powering disks up and down becomes a problem if they are FC-, SAS- or SCSI-based. These disks are made to be powered up and run 7x24 for a few years without spinning down. However, the popular desktop SATA drives are designed to be powered up and down. Manufacturers ratings and lab tests confirm ~ 30,000 power up/down operations can be expected from SATA devices.
To date this point has not been effectively communicated by the industry and misperceptions persist. With a MAID array, no more than 25% of all drives are powered up at any given time, significantly lowering power consumption while prolonging the life (MTBF) of the disk drives. The acquisition cost of MAID subsystems is lowered as the MAID controller has to support only 25% of the memory, I/O connections, and total devices at one time. Today MAID is best suited for WORSE (Write-Once-Read-Seldom-if-Ever) applications and not high-performance tier 1 workloads.
Editor's Note: The MAID concept has kicked off much discussion in the industry. While many believe MAID is not the sole answer, several technology suppliers have begun to look at not just MAID per se, but adding the intelligence to spin down drives that are unused. This spin down concept is expected to permeate into many levels of storage systems, from the device, to the array hardware and software function.
Action Item: Misunderstandings about MAID have slowed its market impact to date. MAID suppliers need to develop a compelling marketing message and crisper positioning to realize the full impact and benefits of this potentially beneficial technology.
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