Massive array of idle disks
Encyclopedia
In computing
, a massive array of idle disks (more commonly known as a MAID) is a system using hundreds to thousands of hard drives for nearline storage
of data
. MAID is designed for 'Write Once, Read Occasionally' (WORO) applications. In a MAID each drive is only spun up on demand as needed to access the data stored on that drive. This is not unlike a very large 'Just a Bunch Of Disks' (JBOD) but with power management.
Compared to RAID technology a MAID has increased storage density, and decreased cost, electrical power, and cooling requirements. However, these advantages are at the cost of much increased latency, significantly lower throughput
, and decreased redundancy. Low drive utilization rates may actually reduce reliability in consumer-oriented large PATA and SATA drives. Drives designed for multiple spin-up/down cycles (e.g. laptop
drives) are significantly more expensive. Latency may be as high as tens of seconds. MAID can supplement or replace tape libraries
in hierarchical storage management
.
To allow a more gradual tradeoff between access time and power savings, some MAIDs such as Nexsan's AutoMAID incorporate disks capable of spinning down to a lower speed, such as 4000 RPM; this achieves 60% of the power reduction achieved by a full spin-down and sleep, and requires less power and time to spin back up to operating speed.
With the advent of SATA
disk drives that are designed to be powered on and off, MAID architecture has evolved into a new storage platform for long term, online storage of persistent data
. Large scale disk storage systems based on MAID architectures allow dense packaging of drives and are designed to have only 25% of disks spinning at any one time.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, a massive array of idle disks (more commonly known as a MAID) is a system using hundreds to thousands of hard drives for nearline storage
Nearline storage
Nearline storage is a term used in computer science to describe an intermediate type of data storage that represents a compromise between online storage and offline storage/archiving...
of data
Data
The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which...
. MAID is designed for 'Write Once, Read Occasionally' (WORO) applications. In a MAID each drive is only spun up on demand as needed to access the data stored on that drive. This is not unlike a very large 'Just a Bunch Of Disks' (JBOD) but with power management.
Compared to RAID technology a MAID has increased storage density, and decreased cost, electrical power, and cooling requirements. However, these advantages are at the cost of much increased latency, significantly lower throughput
Throughput
In communication networks, such as Ethernet or packet radio, throughput or network throughput is the average rate of successful message delivery over a communication channel. This data may be delivered over a physical or logical link, or pass through a certain network node...
, and decreased redundancy. Low drive utilization rates may actually reduce reliability in consumer-oriented large PATA and SATA drives. Drives designed for multiple spin-up/down cycles (e.g. laptop
Laptop
A laptop, also called a notebook, is a personal computer for mobile use. A laptop integrates most of the typical components of a desktop computer, including a display, a keyboard, a pointing device and speakers into a single unit...
drives) are significantly more expensive. Latency may be as high as tens of seconds. MAID can supplement or replace tape libraries
Tape library
In computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device which contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges and an automated method for loading tapes...
in hierarchical storage management
Hierarchical storage management
Hierarchical storage management is a data storage technique which automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as hard disk drive arrays, are more expensive than slower devices, such as optical discs and magnetic...
.
To allow a more gradual tradeoff between access time and power savings, some MAIDs such as Nexsan's AutoMAID incorporate disks capable of spinning down to a lower speed, such as 4000 RPM; this achieves 60% of the power reduction achieved by a full spin-down and sleep, and requires less power and time to spin back up to operating speed.
With the advent of SATA
Sata
Sata is a traditional dish from the Malaysian state of Terengganu, consisting of spiced fish meat wrapped in banana leaves and cooked on a grill.It is a type of Malaysian fish cake, or otak-otak...
disk drives that are designed to be powered on and off, MAID architecture has evolved into a new storage platform for long term, online storage of persistent data
Persistent data
Persistent Data denotes information that is infrequently accessed and not likely to be modified.The opposite of this is dynamic data where information is asynchronously changed as further updates to the information become available. Updates to dynamic data may come at any time, with periods of...
. Large scale disk storage systems based on MAID architectures allow dense packaging of drives and are designed to have only 25% of disks spinning at any one time.