Nearline storage, a contraction of the words "near" and "online," is a computer storage medium that rests between online and offline storage but is closer to online. In this sense, online and offline do not refer to Internet usage but to how the storage medium is used. Online medium is in the computer; offline requires human intervention and mounting, while nearline storage requires some human intervention but is mostly done by the computer. Nearline is not as quick as online storage, but there is only a several-seconds delay before the datum is accessible. The three main types of nearline mediums are magnetic tapes, magnetic disks and compact discs (CD).
The two main types of storage are online and offline. Online refers to storage systems localized on the computer, such as the hard drive, which requires no human intervention. Offline storage is a removable medium that must be hooked up and calibrated to the computer; is very slow but is able to hold massive amounts of memory for archival purposes.
Nearline storage rests between these two. It is like offline storage, because the user does have to place the storage medium in the computer. In the online sense, the computer is doing most of the work, as it knows how to locate the data and also how to retrieve them. Speed-wise, nearline also rests between the two. It is not as slow as offline storage, nor is it as quick as online, but it only has a short delay before the user can manipulate the files in the medium.
Businesses and large data centers are the main proponents of nearline storage, because it helps their databases optimize performance. When a nearline medium is used to archive data, it means the database can stop using energy on those data and work on other functions. At the same time, if the administrator uploads data from the nearline back into the database, this will take much longer and can cause detrimental performance. Consumers also use nearline but are usually offered smaller storage mediums than businesses use.
There are three different forms of nearline storage. The magnetic tape is much like archival tape, but is optimized for nearline use, so it does not require the same amount of preparation to use. The magnetic disk, such as the floppy disk, improves on speed and storage amount. The last of the nearline media is the CD, which is used for data storage in many sectors.