Nearline storage
Encyclopedia
Nearline 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/archiving (used for backups or long-term storage, with infrequent access to data). 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
or optical jukebox
) and put it into a tape drive
or optical disc drive to enable access by bringing the data it contains online. This process is not instantaneous, but it only requires a few seconds.
Both archiving and nearline allow a reduction of database size that results in improved speed of performance for the online system. However, accessing archived data is more complex and/or slower than is the case with nearline storage, and can also negatively affect the performance of the main database, particularly when the archive data must be reloaded into that database.
In addition, some storage systems vendors and suppliers appear to be using the term in reference to low-rotational speed hard drives. Specifically it is being used to refer to high-capacity Serial ATA
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.
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...
or optical jukebox
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 disc and can provide terabytes and petabytes of tertiary storage. The devices are often called optical disk libraries, robotic...
) and put it into a tape drive
Tape drive
A tape drive is a data storage device that reads and performs digital recording, 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 long archival stability.A tape drive provides...
or optical disc drive to enable access by bringing the data it contains online. This process is not instantaneous, but it only requires a few seconds.
Both archiving and nearline allow a reduction of database size that results in improved speed of performance for the online system. However, accessing archived data is more complex and/or slower than is the case with nearline storage, and can also negatively affect the performance of the main database, particularly when the archive data must be reloaded into that database.
In addition, some storage systems vendors and suppliers appear to be using the term in reference to low-rotational speed hard drives. Specifically it is being used to refer to high-capacity Serial ATA
Serial ATA
Serial ATA is a computer bus interface for connecting host bus adapters to mass storage devices such as hard disk drives and optical drives...
drives that work with Serial Attached SCSI
Serial Attached SCSI
Serial Attached SCSI is a computer bus used to move data to and from computer storage devices such as hard drives and tape drives. SAS depends on a point-to-point serial protocol that replaces the parallel SCSI bus technology that first appeared in the mid 1980s in data centers and workstations,...
storage devices. Presumably this usage is by analogy to the high-capacity and low-access speed tape systems.