MAID, or massive array of idle disks, has the potential to make disk-based storage the archive technology of choice in the future.
The selling point of MAID is that it delivers performance in the hard-drive-array class when data is requested yet reduces the amount of energy wasted when archive data is in idle mode . The reduction in power consumption and heat that the MAID model provides puts disk almost in the energy-efficiency class of tape.
MAID products are disk-based archives with unique capabilities that not only minimize power consumption but also prolong the lives of hard drives. The MAID concept has been around for a while, but there is currently only one company delivering live MAID solutions: Copan Systems.
As utility costs and the demand for rapid data access continue to rise, MAID could become even more compelling for long-term storage archiving.
At any given time, only about 25 percent of the disks in a MAID archive are active, with the other 75 percent in an idle state. A MAID system will consume about one-fourth to one-fifth the amount of power of a standard hard-drive-based archive, depending on how often data is accessed.
MAID naysayers often bring up the issue of stiction (static friction) when explaining why MAID is not currently widely used. Stiction is defined as a hard drive failure that occurs when the heads of a hard drive do not lift when platters are spun up. Stiction most often occurs when a hard drive is activated after a long period of inactivity.
Indeed, unlike tape, hard drives were not designed to sit idle for long periods of time. Copan therefore integrated automation programs in its MAID products that exercise the hard disks in an archive from time to time. Copans appropriately named Disk Aerobics technology periodically spins up idle disks and runs consistency checks to ensure that the data residing on the drives is valid.
Disk Aerobics is a novel concept, and it will likely help make sure stiction problems do not occur. However, MAID products are still in their infancy, so IT managers would be right to be somewhat doubtful about the expected life span of a MAID archive.
Copans MAID offerings, including the Revolution 220 family of products, use RAID 5 to ensure that data is protected, even if a drive happens to fail. eWEEK Labs assumes that RAID 6 could be implemented to provide dual parity, ensuring that data would not be lost even in the event that two drives in a given RAID set die simultaneously. When we spoke to Copan officials, however, they said they have no immediate plans to move to RAID 6 because their reliability record has been strong so far.
Copans first archive unit, released in August 2004, functioned as a VTL (virtual tape library), and the company has since added file-share-level access to its MAID archives. The smallest Copan system comes in at 28TB; priced at $3.75 per gigabyte, that makes it about $108,000.