Nearline storage (a
portmanteau
A portmanteau word, or portmanteau (, ) is a blend of words[near
NEAR or Near may refer to:
People
* Thomas J. Near, US evolutionary ichthyologist
* Near, a developer who created the higan emulator
Science, mathematics, technology, biology, and medicine
* National Emergency Alarm Repeater (NEAR), a former ...](_blank)
" and "
online
In computer technology and telecommunications, online indicates a state of connectivity and offline indicates a disconnected state. In modern terminology, this usually refers to an Internet connection, but (especially when expressed "on line" or ...
storage") is a term used
in computer science to describe an intermediate type of data storage that represents a compromise between
online storage (supporting frequent, very rapid access to data) and
offline storage
Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The central processing unit (CPU) of a computer ...
/archiving (used for backups or long-term storage, with infrequent access to data).
Nearline storage dates back to the
IBM 3850
The IBM 3850 Mass Storage System (MSS) was an online tape library used to hold large amounts of infrequently accessed data. It was one of the earliest examples of nearline storage.
History
Starting in the late-1960s IBM's lab in Boulder, Color ...
Mass Storage System (MSS)
tape library
In computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device that contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges a ...
, which was announced in 1974.
Overview
The formal distinction between online, nearline, and offline storage is:
* Online storage is immediately available for input/output (I/O).
* Nearline storage is not immediately available, but can be made online quickly without human intervention.
* Offline storage is not immediately available, and requires some human intervention to become online.
For example, always-on spinning
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
s are online storage, while spinning drives that spin down automatically, such as in massive arrays of idle disks (
MAID
A maid, or housemaid or maidservant, is a female domestic worker. In the Victorian era domestic service was the second largest category of employment in England and Wales, after agricultural work. In developed Western nations, full-time maids ...
), are nearline storage. Removable media such as tape cartridges that can be automatically loaded, as in tape libraries, are nearline storage, while tape cartridges that must be manually loaded are offline storage.
Robotic nearline storage
![StorageTek Powderhorn tape library](https://upload.wikimedia.org/wikipedia/commons/c/c9/StorageTek_Powderhorn_tape_library.jpg)
The nearline storage system knows on which volume (cartridge) the data resides, and usually asks a robot to retrieve it from this physical location (usually: a
tape library
In computer storage, a tape library, sometimes called a tape silo, tape robot or tape jukebox, is a storage device that contains one or more tape drives, a number of slots to hold tape cartridges, a barcode reader to identify tape cartridges a ...
or
optical jukebox
An optical jukebox is a robotic data storage device that can automatically load and unload optical discs, such as Compact Disc, DVD, Ultra Density Optical or Blu-ray and can provide terabytes (TB) or petabytes (PB) of tertiary storage. The device ...
) and put it into a
tape drive
A tape drive is a data storage device that reads and writes data on a magnetic tape. Magnetic tape data storage is typically used for offline, archival data storage. Tape media generally has a favorable unit cost and a long archival stability.
...
or
optical disc drive
In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only r ...
to enable access by bringing the data it contains online.
This process is not instant, but it only requires a few seconds.
Nearline tape and optical storage has the advantage of relatively longer lifespans compared to spinning hard drives, simply due to the storage media being idle and usually stored in protected dust-free enclosures when not in use. In a robotic tape loading system, the tape drive used for accessing data experiences the most wear and may need occasional replacement, but the tapes themselves can last for years to decades. If there are sealable access doors between the access mechanism and the media, it is possible for the idle media storage enclosure to survive fire, floods, lightning strikes, and other disasters.
Hard disk drive nearline storage
MAID
A maid, or housemaid or maidservant, is a female domestic worker. In the Victorian era domestic service was the second largest category of employment in England and Wales, after agricultural work. In developed Western nations, full-time maids ...
(massive array of idle drives) systems archive data in an array of
hard disk drive
A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magnet ...
s, with most drives in a MAID usually stopped. The MAID system spins up each drive on demand when necessary to read (or in some cases to write) data on that drive. For a given amount of storage capacity, MAID systems have higher densities and
lower power and cooling requirements than "hot" storage systems that keep all the disks spinning at full speed at all times.
Some hard drive and storage systems vendors and suppliers use the term in reference to low-rotational speed hard drives that are built to be more reliable than generic desktop and laptop computer hard drives. They are intended to be operational continuously for 24 hours a day, seven days a week, possibly for several years.
Nearline hard drives may be used in personal or small business
network-attached storage
Network-attached storage (NAS) is a file-level (as opposed to block-level storage) computer data storage server connected to a computer network providing data access to a heterogeneous group of clients. The term "NAS" can refer to both the tech ...
(NAS) systems, or as non-critical moderate-performance data storage on servers, where greater durability is required for the drive to operate continuously.
By comparison, standard hard drives are assumed to only be in operation for a few hours each day, and are not spinning when the computer is either turned off or in sleep mode. Standard hard drives may also use data caching methods that can improve single-drive performance, but would interfere with the operation of multi-drive
RAID
Raid, RAID or Raids may refer to:
Attack
* Raid (military), a sudden attack behind the enemy's lines without the intention of holding ground
* Corporate raid, a type of hostile takeover in business
* Panty raid, a prankish raid by male college ...
storage systems, potentially causing data loss or corruption.
Specifically the term ''nearline hard drive'' is being used to refer to high-capacity
Serial ATA
SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard t ...
drives that work with
Serial Attached SCSI storage devices. Presumably this usage is by analogy to the high-capacity and low-access speed tape systems.
[Seagate Technology Paper TP-543 (2005)]
Retrieved on 2012-08-28.
References
{{Reflist, 30em
Computer data storage