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The IBM 3850 Mass Storage System [1] (MSS) was an online tape library used to hold large amounts of infrequently accessed data. [2] It was one of the earliest examples of nearline storage. [3]
Starting in the late-1960s IBM's lab in Boulder, Colorado began development of a low-cost mass storage system based on magnetic tape cartridges. The tapes would be accessed automatically by a robot (known as an accessor) and fed into a reader/writer unit that could work on several tapes at the same time. Originally the system was going to be used as a directly attached memory device, but as the speed of computers grew in relation to the storage, the product was re-purposed as an automated system that would offload little-used data from hard disk systems. Known internally as Comanche while under development, IBM management found a number of niche uses for the concept, and announced it officially as the IBM 3850 on October 9, 1974. After more than a decade (comparable to the IBM 2321 Data Cell, 1964–1975), it was withdrawn August 5, 1986.
The Mass Storage System consisted of a library of cylindrical plastic cartridges, two inches wide and 4 inches (100 mm) long, each holding a spool of tape 770 inches (20 m) long storing 50 MB; each virtual disk required a pair of cartridges. These cartridges were held in a hexagonal array of bins in the IBM 3851 Mass Storage Facility. New cartridges were rolled into the facility and were automatically stored in a vacant bin. The data were accessed via virtual IBM 3330 disk drives, and physically cached on a combination of 3330 and 3350 [lower-alpha 1] staging drives, the data being transferred automatically between cartridge and disk drive in processes called staging and destaging. These were all connected together with the IBM 3830 Storage Control (also used for disk storage alone), the entire system making up a 3850 unit.
Cartridges were moved into and out of read stations by two motorized accessor arms, electrically connected via flat cable on a drum. Stage time for data from cartridge to disk was typically 15 seconds, including about two seconds to move the cartridge into a read station, and eight to ten seconds to read the 200-foot tape.
The recording method was unusual for its time. The drive pulled the tape from the cartridge and wound it once around a cylindrical mandrel in a helix, then stopped the tape. The drive's head, mounted on a rotating drum, then rotated once to read or record a diagonal track. The drive then wound the tape a small step forward and the head rotated to do the next track. Depending on technical definitions this might be even considered a first example of a digital helical scan recording, long before Exabyte's helical drive (which was based on analog video helical recording systems developed earlier).
When free disk space was required a group of cylinders were selected to be destaged to tape, these were transferred with minimal or no change of format. Each tape could store 202 cylinder images of 19 tracks each, half of the 404 cylinders in a 3330 disk pack. Cylinder locations on the tape were fixed and identified by markers along the edge.
Several models of the 3851 were available. The smallest A1 holding 706 cartridges storing 35.3GB, while the largest A4 held 4,720 cartridges storing 236GB in a 20-foot (6.1 m) long unit. All of the units were also available in the "B models" which added a second controller for on-line backups, as well as offline storage. A second series was released on March 6, 1980, doubling maximum capacity to 472GB. The entire series was discontinued on August 5, 1986.
Computer data storage or digital 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.
Disk storage is a data storage mechanism based on a rotating disk. The recording employs various electronic, magnetic, optical, or mechanical changes to the disk's surface layer. A disk drive is a device implementing such a storage mechanism. Notable types are hard disk drives (HDD), containing one or more non-removable rigid platters; the floppy disk drive (FDD) and its removable floppy disk; and various optical disc drives (ODD) and associated optical disc media.
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.
In computing, mass storage refers to the storage of large amounts of data in a persisting and machine-readable fashion. In general, the term "mass" in "mass storage" is used to mean "large" in relation to contemporaneous hard disk drives, but it has also been used to mean "large" relative to the size of primary memory as for example with floppy disks on personal computers.
IBM manufactured magnetic disk storage devices from 1956 to 2003, when it sold its hard disk drive business to Hitachi. Both the hard disk drive (HDD) and floppy disk drive (FDD) were invented by IBM and as such IBM's employees were responsible for many of the innovations in these products and their technologies. The basic mechanical arrangement of hard disk drives has not changed since the IBM 1301. Disk drive performance and characteristics are measured by the same standards now as they were in the 1950s. Few products in history have enjoyed such spectacular declines in cost and physical size along with equally dramatic improvements in capacity and performance.
Linear Tape-Open (LTO), also known as the LTO Ultrium format, is a magnetic tape data storage technology used for backup, data archiving, and data transfer. It was originally developed in the late 1990s as an open standards alternative to the proprietary magnetic tape formats that were available at the time. Upon introduction, LTO rapidly defined the super tape market segment and has consistently been the best-selling super tape format. The latest generation as of 2021, LTO-9, can hold 18 TB in one cartridge.
In computer storage, a tape library is a physical area that holds magnetic data tapes. In an earlier era, tape libraries were maintained by people known as tape librarians and computer operators and the proper operation of the library was crucial to the running of batch processing jobs. Although tape libraries of this era were not automated, the use of tape management system software could assist in running them.
Hierarchical storage management (HSM), also known as tiered storage, is a data storage and data management technique that automatically moves data between high-cost and low-cost storage media. HSM systems exist because high-speed storage devices, such as solid-state drive arrays, are more expensive than slower devices, such as hard disk drives, optical discs and magnetic tape drives. While it would be ideal to have all data available on high-speed devices all the time, this is prohibitively expensive for many organizations. Instead, HSM systems store the bulk of the enterprise's data on slower devices, and then copy data to faster disk drives when needed. The HSM system monitors the way data is used and makes best guesses as to which data can safely be moved to slower devices and which data should stay on the fast devices.
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.
In computing, external storage refers to non-volatile (secondary) data storage outside a computer's own internal hardware, and thus can be readily disconnected and accessed elsewhere. Such storage devices may refer to removable media, compact flash drives, portable storage devices, or network-attached storage. Web-based cloud storage is the latest technology for external storage.
Storage Technology Corporation created several magnetic tape data storage formats. These are commonly used with large computer systems, typically in conjunction with a robotic tape library. The most recent format is the T10000. StorageTek primarily competed with IBM in this market, and continued to do so after its acquisition by Sun Microsystems in 2005 and as part of the Sun Microsystems acquisition by Oracle in 2009.
In 1953, IBM recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost. After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc., the engineers at IBM's San Jose California laboratory invented the hard disk drive. The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory but faster and more expensive than tape drives.
Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording.
Count key data (CKD) is a direct-access storage device (DASD) data recording format introduced in 1964, by IBM with its IBM System/360 and still being emulated on IBM mainframes. It is a self-defining format with each data record represented by a Count Area that identifies the record and provides the number of bytes in an optional Key Area and an optional Data Area. This is in contrast to devices using fixed sector size or a separate format track.
In IBM mainframe operating systems OS/360 and its successors, a Unit Control Block (UCB) is a memory structure, or a control block, that describes any single input/output peripheral device (unit), or an exposure (alias), to the operating system. Certain data within the UCB also instructs the Input/Output Supervisor (IOS) to use certain closed subroutines in addition to normal IOS processing for additional physical device control.
The Linear Tape File System (LTFS) is a file system that allows files stored on magnetic tape to be accessed in a similar fashion to those on disk or removable flash drives. It requires both a specific format of data on the tape media and software to provide a file system interface to the data.
The IBM Administrative Terminal System (ATS/360) provided text- and data-management tools for working with documents to users of IBM System/360 systems.
John Mason "Jack" Harker was an inventor, mechanical engineer, and product and program manager who pioneered development of disk storage systems. Starting as a member of the original team that developed the first disk storage system, he went on to develop IBM Direct Access Storage products for the next 35 years. Over that time, Harker was twice director of the IBM San Jose Storage Laboratories, an IBM Fellow, and an IEEE Fellow. He retired from IBM in 1987 and died in 2013.
Beginning with its 1964 System/360 announcement, IBM's mainframes initially accessed count key data (CKD) subsystems via a channel connected to separate Storage Control Units (SCUs) with attached Direct Access Storage Devices (DASD), typically a hard disk drive. This practice continued in IBM's larger mainframes thru IBM Z; however low end systems generally used lower cost integrated attachments where the function of the SCU was combined with that of the channel, typically called an Integrated File Adapter.
A track is a path on a recording medium. There are some variations in nomenclature; for some media a track is a logical path and for others it is based on the geometry of the medium. The term is not used for punched cards.
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