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History of IBM magnetic disk drives

From Alfawiki
IBM Magnetic Disk Storage Division
Company typeDivision
IndustryComputer storage
Founded1956
Defunct2003
FateDivested to Hitachi
ProductsHard disk drives, floppy disk drives
ParentIBM

IBM was a producer of magnetic disk storage equipment from 1956 until 2003, at which point it divested its hard disk drive division to Hitachi. IBM’s workforce was responsible for inventing both the hard disk drive (HDD) and the floppy disk drive (FDD), contributing numerous technological advancements in these fields. The fundamental mechanical architecture of hard disk drives has remained largely unchanged since the introduction of the IBM 1301, with performance benchmarks adhering to consistent standards dating back to the 1950s. Over time, these devices have experienced significant reductions in cost and physical dimensions while achieving notable gains in storage capacity and operational efficiency.

IBM manufactured 8-inch floppy disk drives from 1969 through the mid-1980s but did not become a dominant supplier of smaller form factors such as the 5.25- or 3.5-inch drives. Although IBM sold its magnetic disk drives directly, it only started offering them under original equipment manufacturer (OEM) agreements beginning in 1981. By 1996, IBM had ceased producing HDDs exclusively for its own systems, transitioning entirely to OEM distribution.

IBM has referred to its magnetic disk products using various terms including direct-access storage device (DASD), disk file, and diskette file; however, this article employs the industry-standard designations hard disk drive (HDD) and floppy disk drive (FDD).

IBM 350

The IBM 350 disk storage unit, recognized as the first-ever disk drive, was introduced on September 14, 1956, as a component of the IBM 305 RAMAC computer system. A related model, the IBM 355, was also announced for use with the IBM 650 RAMAC system. The acronym RAMAC stood for "Random Access Method of Accounting and Control." The initial prototype was delivered to Zellerbach Paper Company in June 1956, with production units shipped starting November 1957 to clients including United Airlines.

Engineered to facilitate real-time business accounting processes, the IBM 350 offered storage capacity for five million characters encoded in six bits each (equivalent to approximately 3.75 MB). It comprised fifty-two disks measuring 24 inches in diameter, utilizing one hundred recording surfaces rotating at a speed of 1200 revolutions per minute. Data transfer rates reached up to 8,800 characters per second. The drive’s access mechanism allowed vertical and radial movement of read/write heads to select specific tracks on the disks. Several enhanced versions were launched throughout the late 1950s. The IBM RAMAC 305 system equipped with the 350 disk was leased at $3,200 monthly. Production of the IBM 350 concluded in 1969.

The patent originating from the RAMAC initiative is regarded as the foundational intellectual property for disk drive technology. Although initially rejected by IBM’s Board over concerns about potential impacts on its punch card business, development persisted until receiving approval from IBM’s president.

The physical dimensions of the unit measured approximately 60 inches in length, stood 68 inches tall, and was 29 inches wide, weighing around one ton—requiring forklift assistance for relocation. Currie Munce, former research vice president at Hitachi Global Storage Technologies (which acquired IBM's storage operations), noted that although capacity could have surpassed five million characters, marketing hesitated to promote higher-capacity models. Nonetheless, double-capacity versions were announced in January 1959 and shipped later that same year.

In recognition of its historical significance, the RAMAC 350 Disk File was declared an International Historic Landmark by The American Society of Mechanical Engineers in 1984. A restoration effort commenced in 2002 under Al Hoagland’s leadership in partnership with Santa Clara University. Since its restoration completion in 2005, the RAMAC has been displayed at the Computer History Museum located in Mountain View, California.

IBM 353

The IBM 353, employed in the IBM 7030, bore resemblance to the IBM 1301 but offered an enhanced data transfer speed. It provided storage for 2,097,152 (221) words of 64 bits each (totaling 134,217,728 bits) and achieved a transfer rate of 125,000 words per second. A prototype delivered in late 1960 was pioneering as the first disk drive to utilize one read/write head per surface that floated on compressed air, akin to the earlier IBM 350 design. Production versions incorporated self-levitating heads similar to those found in the IBM 1301.

IBM 355

Unveiled on September 14, 1956, the IBM 355 broadened storage capabilities for the IBM 650. Utilizing the IBM 350 mechanism, it featured up to three access arms—an increase from the single arm on the IBM 350—and held a capacity of six million decimal digits plus 600,000 sign characters. This device moved entire tracks between its magnetic storage and the core memory of the 653 option for the IBM 650, which offered sixty signed 10-digit words—adequate for a single track or tape record.

IBM 1405

Launched in 1961 for use with the IBM 1400 series business computers, the IBM 1405 Disk Storage Unit was available in two variations. Model 1 accommodated 10 million alphanumeric characters (60 million bits) across 25 disks; Model 2 doubled this capacity with 20 million characters (120 million bits) over 50 disks. The disks rotated vertically at a speed of 1200 revolutions per minute.

Each disk surface contained 200 tracks segmented into five sectors, numbered from 0 to 4 on the upper side and from 5 to 9 on the lower side. Each sector stored between 178 and 200 characters. One to three forked access arms were equipped with two read/write heads each to service both top and bottom surfaces. The arms moved vertically to select among disks (0–49) and horizontally to choose tracks (0–199). Sector read or write operations took approximately ten milliseconds.

Access latency ranged from a minimum of about 100 milliseconds up to a maximum of roughly 700 milliseconds for Model 1 and up to 800 milliseconds for Model 2. Model 2 contained around 100,000 sectors capable of holding either 200 characters in move mode or, in load mode, stored 178 characters plus a word mark bit per character. Model 1 had half this number of sectors.

IBM 7300

The IBM 7300 Disk Storage Unit was engineered specifically for the IBM 7070 system; its model 2 variant was introduced in 1959. Nonetheless, following the release of the 1301 in June of 1961, many users of the IBM 7070 and IBM 7074 gravitated toward the newer unit. The technology underpinning the IBM 7300 shared similarities with that employed in the IBM 350, IBM 355, and IBM 1405 models.

IBM 1301

Announced on June 2, 1961, the IBM 1301 Disk Storage Unit was designed for use with the IBM mainframe series as well as the IBM 1410. Each module stored approximately twenty-eight million characters (twenty-five million when paired with the IBM 1410), utilizing twenty-five large disks with forty recording surfaces accessible to users and featuring two hundred fifty tracks apiece. The Model 1 consisted of a single module; Model 2 stacked two modules vertically. Disks revolved at a speed of eighteen hundred rpm, enabling data transfer rates up to ninety thousand characters per second.

A notable advancement was its design featuring an individual arm and read/write head dedicated to each recording surface; these moved collectively in unison resembling a comb mechanism. This innovation minimized seek times by removing delays caused by repositioning heads across disks, resulting in an average access time capped at one hundred eighty milliseconds. Additionally, it was pioneering as the first disk drive to employ aerodynamically shaped heads that fly on a thin cushion of air, allowing closer proximity to disk surfaces and thereby enhancing performance.

Connection was established through the IBM 7631 File Control unit, which supported operation either with an IBM 1410 or systems from the IBM 7000 series, including configurations allowing shared usage between two separate systems.

Leasing prices for the IBM 1301 Model 1 were set at $2,100 monthly or $115,500 for purchase; Model 2 cost $3,500 per month or $185,000 to acquire. The IBM 7631 controller leased at $1,185 per month or could be bought for $56,000. All versions were discontinued by around 1970.

IBM 1302

Launched in September 1963, the IBM 1302 Disk Storage Unit introduced enhanced recording technology that increased its capacity fourfold compared to the IBM 1301, reaching 117 million 6-bit characters per module. It delivered an average access time of 165 milliseconds and a data transfer speed of 180,000 characters per second, which is more than twice the rate of the 1301. Each module was equipped with two separate access mechanisms dedicated to the inner and outer cylinders. The Model 2 variant doubled the storage capacity by stacking two modules together. Leasing fees were set at $5,600 per month for Model 1 and $7,900 per month for Model 2; purchase prices were $252,000 and $355,500 respectively. The optional IBM 7631 controller added an extra $1,185 monthly or $56,000 if purchased outright. The IBM 1302 was discontinued in February 1965.

IBM 1311

Introduced in October 1962, the IBM 1311 Disk Storage Drive targeted medium-scale business and scientific computing needs. Roughly the size of a top-loading washing machine, it utilized a removable IBM 1316 disk pack capable of storing 2 million characters. Throughout the 1960s, seven different models were released before being phased out by the early 1970s.

Each IBM 1316 disk pack contains six disks measuring 14 inches in diameter, providing ten usable recording surfaces in total. Operating at 1500 revolutions per minute, each surface includes 100 tracks with 20 sectors per track; each sector holds 100 characters. The disk pack is housed within a transparent plastic casing featuring a locking handle to ensure secure installation and removal—a design that influenced many subsequent disk packs.

The seven IBM 1311 models comprised both master drives (which included controllers) and slave drives (which did not). Master drives could manage multiple slave drives depending on system compatibility:

  1. Master drive for IBM 1440/1460/1240 systems, supporting up to four slaves; retired in 1971.
  2. Slave drive compatible with master features; withdrawn in 1975.
  3. Master drive for IBM 1620/1710 systems, managing up to three slaves; phased out in 1971.
  4. Master drive for IBM 1401 systems with support for four slaves; discontinued in 1971.
  5. Master drive designed for IBM 1410/7010/7740 systems featuring standard Direct Seek; withdrawn in 1971.
  6. & #7 Details are unclear but likely correspond to master and slave drives; both retired by early 1970s.

Available optional enhancements included:

  • Direct Seek—removes the need to return to track zero before seeking a new track.
  • Scan Disk—enables automated rapid searching for specific identifiers or conditions.
  • Seek Overlap—allows concurrent seek operations and read/write activities across multiple drives.
  • Track Record—increases storage capacity by recording one large record per track instead of multiple smaller sectors, significantly raising total bits stored.

Master drives (Models 1,3,4,5) incorporate additional power supplies and control circuitry and are approximately one foot wider than Model 2 slave drives.

IBM 2302

The IBM 2302 serves as the System/360 counterpart to the IBM 1302, redesigned to fit the S/360 DASD architecture. It uses a non-removable module containing 25 platters with a total of 46 recording surfaces. The Model 3 configuration includes a single module, whereas Model 4 contains two modules. Each module is equipped with two independent access mechanisms covering the innermost and outermost spans of 250 cylinders—referred to as access groups—each featuring one read/write head per track. Average rotational latency is approximately 17 milliseconds with a maximum delay of up to 34 milliseconds; maximum seek time within each access group is around 180 milliseconds. Tracks hold about 4,985 bytes each, resulting in an overall module capacity of roughly 112 megabytes. Connection to IBM mainframe systems is facilitated via the IBM 2841 Storage Control Unit.

IBM 2305

Released in 1970, the IBM 2305 fixed-head storage unit was introduced alongside the IBM 2835 Storage Control for use with System/360 models 85 and 195, interfacing through the IBM 2880 Block Multiplexor Channel.

During the System/370 period, the 2305 gained popularity as a paging storage device due to its rapid access speeds. It supported a range of systems including the 3155, 3165, 3158, 3168, 3033, 4341, and the 3081 (the latter utilizing specialized microcode). The device was also suited for managing small, frequently accessed data sets such as catalogs and job queues in environments with heavy workloads.

The 2305-1 model delivers a storage capacity of 5.4 MB and transfers data at a rate of 3.0 MB/s via a two-byte channel interface, featuring an average access latency of 2.5 milliseconds. The larger-capacity 2305-2 offers 11.2 MB with a data rate of 1.5 MB/s and an average access time of approximately 5 milliseconds.

Engineered for swift and continuous retrieval of modest-sized data volumes, the 2305’s combination of speed and capacity made it ideal for system-resident functions including work files, job queues, indices, and other frequently referenced datasets. Its rapid response times proved especially beneficial in systems experiencing high transaction volumes.

IBM 2311

The IBM 2311 Disk Storage Drive debuted in 1964 along with the 2841 Control Unit, targeting the IBM System/360 family while also supporting the IBM 1130 and IBM 1800 systems. It connected directly to models such as the IBM System/360 Model 20 and Model 25. All units utilized the removable IBM 1316 Disk Pack, originally introduced with the IBM 1311.

The Model 1 connects through the 2841 Control Unit to most IBM mainframes; on the System/360 Model 25, connection is established via a Disk Attachment Control unit. The disk packs employ IBM’s count key data variable record length format.

Models 11 and 12 operate with the System/360 Model 20’s integrated control using a fixed sector format. Due to these differing formats, disk packs are not interchangeable between Model 1 drives and Models 11/12.

Mechanically akin to the IBM 1311 but enhanced for greater recording density, the IBM 2311 stores up to 7.25 megabytes on one removable IBM 1316 disk pack comprising six platters spinning as a unit. It features ten read/write heads mounted on a hydraulically actuated arm, with each platter surface containing 200 tracks plus three additional spare tracks for defect management. The drive’s average seek time is approximately 85 milliseconds, while its data transfer speed reaches around 156 kB/s.

Standardized electrical interfaces across various System/360 models allowed third-party vendors to develop plug compatible disk drives, fostering a competitive market for IBM-compatible storage devices.

IBM 2314 Disk Access Storage Facility Model 1

Launched in April 1965, the IBM 2314 was engineered for both System/360 and System/370 platforms. Featuring a Two Channel Switch capability, it could connect simultaneously to two separate channels. While its disk mechanism was similar to that of the IBM 2311, it significantly increased data density.

The system utilized a taller removable IBM 2316 disk pack containing eleven-inch diameter disks (totaling twenty surfaces), capable of storing roughly twenty-nine million characters. Equipped with twenty read/write heads on a hydraulically actuated arm, each surface contained about two hundred tracks. Initial access times were comparable to those of the IBM 2311 but improved over time due to enhancements in hydraulic actuator technology. Data transfer rates were doubled to approximately 310 kB/s.

The original Model 1 configuration consisted of nine disk drives packaged as a single unit along with a storage control unit: one single-drive module plus two four-drive modules. Drives were installed in drawers allowing convenient access to disk packs and earned the nickname "Pizza Ovens" because of their distinctive appearance. Although nine drives were included, only eight could be accessed by the computer simultaneously; the ninth served as an offline spare to enable maintenance without interrupting operations. Drive system addresses were configured using user-swappable plugs, providing flexible assignment options including designating spare units.

An optional IBM 2844 Control Unit allowed two System/360 channels to access separate drives within the facility concurrently.

Subsequent iterations of the IBM 2314 further expanded these foundational features:

IBM 2314 Direct Access Storage System - Variants

In 1969, IBM segmented the 2314 storage system into distinct models, each supporting up to nine drives (with eight available online) connected to a 2314 Storage Control. These included:

  • The 2312 Disk Storage, featuring a single-drive configuration.
  • The 2313 Disk Storage, which incorporated four drives.
  • The 2318 Disk Storage, comprising two drives.

IBM 2319

To compete with plug compatible vendors offering alternatives comparable to the 2314, IBM launched the cost-efficient three-drive 2319 modules in 1970. This was achieved by removing one drive from the four-drive 2313 model and rebranding it as the 2319 A1, marketed with significantly lower rental fees. This approach reduced expenses for new clients while retaining premium pricing for existing users. The 2319-A1 interfaces with integrated controllers designed for System/370 Models 135 and 145, and conventional 2314 DASD units such as the 2312 or 2318 can be attached. The 2319 B series introduced three-drive modules enabling configurations of three, six, or nine drives connected to a novel 2314 Model B Storage Control Unit.

IBM 3310

Released on January 30, 1979, the IBM 3310 Direct Access Storage Device was developed for IBM 4331 midrange computer systems. Each drive provided a storage capacity of 64.5 MB and employed fixed-block architecture (FBA). This device was compatible exclusively with DOS/VSE and VM operating systems on System/370 platforms.

IBM 3330

The IBM 3330 Direct Access Storage Facility, codenamed Merlin, debuted in June 1970 targeting IBM System/370 and System/360 Model 195 environments. Initial offerings included the two-drive Model 1 and single-drive Model 2 units. Each removable disk pack stored 100 MB, featured a 30 ms access time, and supported data transfer speeds of up to 806 kB/s. A significant innovation was the introduction of error correction using fire codes, which improved reliability and reduced costs by allowing tolerance of disk surface defects.

The original configuration consisted of a single storage control unit (3830 Model 1) physically attached to a single 3330 drive, with the option to add up to three additional drives forming an eight-drive chain.

In August 1972, IBM announced the 3830 Model 2 Storage Control along with the 3333 Disk Storage and Control, which separated controller functionality from drive strings. The upgraded 3830 acted as a director-style controller capable of managing multiple strings. The first unit in each string, the 3333, integrated a controller with two drives and supported attachment of up to three additional 3330 drives (eight total). Two such 3333 units could connect to one 3830 Model 2 controller, allowing control over as many as sixteen drives; optional string switches facilitated connection to two separate storage controls.

In 1973, double-density (-11) variants were introduced: the 3333–11, the 3330-11, and larger capacity (200 MB) disk packs labeled as 3336–11. Mixing original and double-density drives within a single string was not supported. Upgrading from base models to Model-11 versions required extensive conversion processes and data migration efforts.

The IBM 3330 was discontinued in 1983.

IBM 3340 and IBM 3344

While sharing many characteristics, the IBM 3340 and IBM 3344 differ in that only the IBM 3340 can function as the head of a drive string. There are no A model versions of the IBM 3344; therefore, any IBM 3344 must be connected under an IBM 3340 A model acting as head of string.

IBM 3340

Introduced in March 1973 for the IBM System/370, the IBM 3340 Direct Access Storage Facility, known by the codename Winchester, came in three variants: the 3340-A2 featuring two drives and a controller, and the B2 (two drives) and B1 (single drive) models. Up to eight B-units could be linked to a single A2 controller.

This system utilized removable data modules that included both the head and arm assembly; during loading or unloading, the module’s access door would open to interface with the drive, eliminating the need to remove a cover as was necessary with previous disk packs. It offered an average access time of 25 milliseconds and a data transfer rate of 885 kB/s. The IBM 3348 Data Module was available in three configurations: one with 35 MB capacity and two with 70 MB, one of which featured 500 KB accessible through fixed heads for quicker data retrieval. The 3340 supported error correction capabilities and was retired from the market in 1984.

Developed under Ken Haughton’s leadership in San Jose, this design initially aimed at two removable modules each holding 30 MB—hence its nickname Winchester, inspired by the Winchester .30-30 rifle. Although storage capacities expanded over time, the code name remained unchanged.

A significant advancement was its economical head design that permitted heads to land and lift off directly from spinning media without unloading, greatly simplifying mechanics and lowering costs. This approach, termed "Winchester technology," set a new standard across the disk drive industry.

The designation Winchester or its abbreviation Winnie was widely used to describe hard drives through the early 1990s but has since largely disappeared from common terminology worldwide.

IBM 3344

Sharing similarities with the IBM 3340, the IBM 3344 employed fixed media rather than removable IBM 3348 data modules. Each spindle housed four logical drives, each matching the storage capacity of a single 3348–70 module. Available exclusively as dual-drive units, it did not include an A (head of string) model. The 3344-B2F variant closely resembled the 3344-B2 but incorporated fixed heads over certain cylinders on both drives. Both models required a 3340-A2 or 3340-A2F unit to serve as head of string. Internally, the IBM 3344’s architecture paralleled that of the IBM 3350; distinctions were confined to differences in microcode within the control unit.

IBM 3350

Launched in 1975 for IBM System/370, the IBM 3350 Direct Access Storage Facility bore the codename Madrid and introduced sealed head-disk assemblies (HDAs) that integrated both head and arm components into a non-removable unit. Its disk configuration—comprising 555 cylinders, 30 heads, and tracks holding 19,069 bytes each—provided roughly 317 MB of storage per HDA. This sealed HDA design became a standard for subsequent IBM DASD products.

Available models included A2, A2F, B2, B2F, C2, and C2F, each containing two HDAs. The A2 and A2F units featured an additional electronic board facilitating connection to control units; these often functioned as controllers or head-of-string devices. Drives were arranged in strings beginning with an A2 or A2F unit followed by up to three B2 units or mixed configurations including C2 units. Typically, the A2 model incorporated a string switch enabling dual links to storage controllers such as the IBM 3830 Model 2 or Integrated Storage Control embedded in processors like the IBM 3148. Later controller models like the IBM 3880 maintained backward compatibility. The C2 unit contained its own controller acting as a backup path if the A unit’s controller failed but offered limited connectivity options.

Permissible IBM 3350 configurations included strings designated as -A, -AB, -ABB, -ABBB, -AC-, -ABC-, and -ABBC-.

Models suffixed with "x2F" (for example, A2F) featured fixed head areas covering the first five cylinders on both HDAs, eliminating seek time within this zone. This capability was designed to optimize access to frequently used checkpoint data for HASP or JES2 spool files and enhance performance for TSO swap areas and system swap files under OS/360 successors such as MVT, SVS, and MVS by reducing head movement during context switches.

The IBM 3350 series was withdrawn from production in September 1994.

IBM 3370

In January 1979, IBM introduced the IBM 3370 Direct Access Storage Device, designed for use with IBM 4331, 4341, and System/38 midrange systems. This model incorporated seven fixed 14-inch platters, delivering a storage capacity of 571 MB per unit. Notably, it was the first hard disk drive to implement thin-film head technology developed at IBM's Thomas J. Watson Research Center. The 3370 utilized a fixed-block architecture and was compatible with DOS/VSE and VM operating systems running on S/370 platforms.

IBM 3375

The IBM 3375, serving as a complementary device, employed count key data (CKD) architecture, which was essential for operating systems such as OS/360 and its derivatives.

IBM 3380

Released on June 11, 1980, the IBM 3380 DASD featured thin-film head technology and provided a capacity of 2.52 GB per unit. Each unit contained two hard disk assemblies equipped with dual actuators, each accessing approximately 630 MB. It supported data transfer rates up to 3 MB per second and had an average access time of 16 milliseconds. Initial pricing ranged between $81,000 and $142,200. Due to tribological challenges involving the interaction between heads and media surfaces, actual shipments commenced in October 1981.

Typical configurations consisted of one A unit paired with up to three B units. Each 3380 housed four devices, enabling a maximum of sixteen devices per string. The device interfaced with IBM 3880 storage control units through two data paths, allowing concurrent I/O operations directed at separate hard disk assemblies.

In February 1985, IBM launched the Extended Capability Models (3380 E) featuring double density and a capacity of 5.04 GB per unit—two actuators each managing 1.26 GB. Subsequently, in August 1987, the Model K was introduced with triple capacity at 7.562 GB per unit (two actuators at 1.89 GB). This model offered an optional four-path mode that supported up to thirty-two devices per string when connected to a 3990 storage control unit.

The entire IBM 3380 series comprised twelve variants: six A-units (which acted as string heads containing controller logic for storage control unit connections), five B-units (which attached to A- or C-units), and one C-unit (providing direct channel connectivity).

Production of the IBM 3380 persisted until May 1996, marking an exceptional fifteen-year lifecycle that surpassed the typical longevity expected of disk drives.

IBM 3390

Debuted in November 1989, the IBM 3390 DASD family offered storage capacities reaching up to 22 gigabytes across multiple drives. System pricing varied widely from $90,000 to $795,000 based on configuration and capacity selected.

A standard IBM 3390 string comprises a central A unit containing four or eight devices, optionally accompanied by one or two B units holding as many as twelve devices each. Operating in four-path mode when connected to a 3990 storage control unit, the system can support an additional 3390 string, allowing up to sixty-four devices within a single subsystem.

Hard Disk Assemblies in this series include two actuator-head units along with platters: Model 1 delivers an unformatted capacity of 1.89 GB; Model 2 doubles this to approximately 3.78 GB per HDA. The Model 3 released in 1991 increased capacity by fifty percent to about 5.67 GB per HDA, while Model 9 introduced in 1993 tripled it further to roughly 11.3 GB per HDA.

Unlike earlier DASD models that utilized large AC motors driving HDAs via belts, the IBM 3390 integrated a DC motor within its enclosure for drive operation. The Model 9 represented IBM’s final announcement of a Single Large Expensive Disk (SLED) drive.

IBM 9345

Released in November 1990 as a Request Price Quotation (RPQ) for IBM's SCSE (SuperComputing Systems Extensions), the IBM 9345 hard disk drive was developed at IBM's San Jose laboratory under the project name Sawmill. It offered capacities up to 1.5 GB within a full-height 5¼-inch enclosure, utilizing as many as eight 130 mm platters. This model was pioneering as the first HDD to employ Magnetoresistive (MR) head technology.

IBM 9340

In October 1991, IBM launched the 9345 DASD as part of the 9340 family of channel-attached count key data (CKD) DASD subsystems, designed for compatibility with IBM mainframe systems such as the ES/9000 series. The Model 1 of the 9345 included two hard drives each with a capacity of 1.0 GB, whereas Model 2 featured two drives with 1.5 GB each.

While functionally akin to the IBM 3990/3390 storage devices, the 9340/9345 lacked the non-volatile RAM cache present in the 3990 and supported a shorter maximum block length compared to the 3390. The operating system's Input/Output Supervisor (IOS) identified these attributes through the IECCINIT initializer, which assigned device types based on cache availability and track size.

9330 Family of Disk Drives

  1. The 9331 Diskette Unit models 1 and 11 were equipped with a single 8-inch floppy disk drive; models 2 and 12 incorporated one 5-inch floppy disk drive.
  2. The 9332 Direct Access Storage Device utilized the IBM 0667 hard disk drive.
  3. The 9333 High Performance Disk Drive Subsystem employed either IBM 0664 or IBM 0681 hard drives depending on the variant.
  4. The 9334 Disk Expansion Unit connected between one and four SCSI hard drives to RS/6000 systems.
  5. The 9335 Direct Access Storage Subsystem featured the "Kestrel" hard drive, engineered at IBM Hursley in the UK—an 850 MB device comprising three 14-inch platters with dual rotary actuators accessing multiple surfaces. This rack-mountable unit debuted in October 1986 alongside the IBM 9370 Information System. No original equipment manufacturer (OEM) versions are documented.
  6. The 9336 Disk Unit incorporated the IBM 0681 hard disk drive, also known as Redwing.
  7. The 9337 Disk Array Subsystem utilized IBM's IBM 0662 (Spitfire) or IBM 0663 (Corsair) hard disk drives.

IBM 2310

The IBM 2310 Removable Cartridge Drive was introduced in conjunction with the IBM 1800 in 1964 and subsequently with the IBM 1130 in 1965, most likely first shipping with the latter late that year. It stored a total of 512,000 words of sixteen bits each (equivalent to 1,024,000 bytes) on an IBM 2315 cartridge. This cartridge contained a single fourteen-inch oxide-coated aluminum platter encased in plastic with openings permitting access for read/write heads.

IBM 5444

Debuting in September of 1969 as part of System/3 and developed at IBM’s Hursley facility in England under the codename Dolphin, the IBM 5444 utilized a disk cartridge designated as the IBM 5440 containing one fourteen-inch platter. This product line included three models:

  • Model 1: featured one fixed and one removable disk, both offering one hundred tracks per surface; cartridge capacity was approximately 1.23 MB
  • Model 2: contained one fixed and one removable disk, each with two hundred tracks per surface; capacity doubled to about 2.46 MB
  • Model 3: consisted solely of one removable disk with two hundred tracks per surface; capacity matched Model 2 at roughly 2.46 MB

IBM 62GV

The IBM 62GV, initially shipped in May of 1974 from IBM’s Hursley lab in the UK (code-named Gulliver), began with a storage capacity of five megabytes. Subsequent versions (62TM) expanded this to ten megabytes and then fourteen megabytes. It employed a Swinging Arm actuator mechanism paired with a single fourteen-inch platter. This actuator design became IBM’s most widely licensed electromechanical innovation and saw extensive adoption across hard drives globally. Approximately one hundred seventy-seven thousand units were shipped, making it the first hard drive to surpass one hundred thousand units sold.

OEM and Small Systems Hard Drives

This segment details hard disk drives produced by IBM, marketed as OEM components and utilized in IBM small systems such as the System/3, System/32, /34, /36, and AS/400. Drives are listed by their OEM model numbers and organized according to their initial customer delivery dates.

IBM 0680

Introduced in 1979, the 0680 was employed in numerous IBM small systems and entry-level System/370 models as the 3310 direct access storage device. Officially announced as the 0680 OEM variant in September 1981, it was engineered at IBM’s Hursley laboratory in the UK under the project name Piccolo. This drive incorporated six 8-inch (210 mm) platters and initially offered storage capacity up to 65MB, featuring an enhanced rotary actuator.

A higher-capacity version known as the 62SW was released in June 1984; however, its market penetration was limited due to a cost per megabyte comparable to that of the 62GV model.

IBM 0676

The 0676 debuted in November 1982 as a 5247 Disk Storage Unit designed for the IBM System/23 Datamaster. Developed at IBM Rochester, Minnesota under the designation 21ED, it was an 8-inch hard disk with starting capacities of either 15 or 30 MB distributed over two or four platters. In 1983, it was integrated into the System/36’s 5360 System Unit. By 1984, its capacity doubled through increased tracks per surface and was incorporated into the System/36’s upgraded 5362 System Unit.

IBM 0665

Released in October 1985 for the PC AT (5170) system unit, the 0665 was developed at IBM Rochester under the codename "Pixie." This model was a 5¼-inch hard disk drive available with storage options of 20, 30, or 44 MB.

IBM 0667

First delivered in August 1986, the 0667 was created at IBM Rochester with the project name "Grant." It was a full-height ESDI hard drive measuring 5¼ inches, accommodating up to four platters of 130 mm diameter and providing a capacity of up to 70 MB. This drive was offered on select PC RT models (6150, 6151, 6152) as well as System/36 Model System Units (5363, 5364).

IBM 0669

The 0669, introduced in 1987 and developed at IBM Rochester under the codename "Grant-Prime," was a full-height hard disk measuring 5 inches with a maximum capacity of approximately 115 MB across four platters of 130 mm diameter. It functioned as the internal drive for both the System/36 model 5363 and the Series 1 model 4956 System Units.

IBM 0671

Unveiled in 1987 and developed under the codename "Lee" at IBM Rochester, the 0671 was an ESDI full-height hard drive measuring five inches with up to eight platters of 130 mm diameter. It offered storage capacities reaching up to 316 MB and represented IBM’s inaugural implementation of a thin metal film recording surface. This drive was incorporated into the IBM AS/400 9404 System Unit released in 1988, supporting configurations of two or three drives.

IBM 0661

The 0661, introduced in 1989 as model number 371, was a SCSI hard disk drive developed under the codename "Lightning" at both IBM Rochester and Hursley laboratories. It featured up to eight platters measuring 95 mm each (with a total of fourteen heads), providing an initial capacity of around 320 MB. A subsequent "Turbo" variant offering approximately 400 MB appeared in 1990. This model became standard equipment within key IBM platforms such as the AS/400 System Unit Model CXX.

IBM 0681

Launched in April 1990 from IBM Hursley under the project name Redwing—the final HDD developed at that facility—the 0681 was a full-height five-inch hard disk with up to twelve platters of 130 mm diameter and storage capacity reaching approximately 857 MB. It introduced PRML (Partial Response Maximum Likelihood) data decoding technology. This drive powered the IBM 9333 Disk Drive Subsystem starting from early shipments in 1992; later that year, a higher-density version providing about 1.07 GB became available in May.

IBM 0663

Introduced in late 1991 under the codename "Corsair," the 0663 was a compact 3-inch half-height (1.6-inch) hard disk drive capable of storing up to 1 GB across eight 95 mm platters. This model appeared in specific PS/2 and RS/6000 systems and marked IBM's initial use of Magnetoresistive (MR) head technology in an OEM drive.

IBM 0664

The 0664, unveiled in November 1992 and developed at IBM Rochester under the codename "Allicat," was a full-height 5-inch hard drive (3.25 inches tall) that effectively combined two 3-inch drives. It provided a maximum capacity of 2.013 GB using as many as eight 95 mm platters.

IBM 0662

Released in June 1993 and known internally as "Spitfire" at IBM Rochester, the 0662 was a full-height (1-inch tall) 3-inch hard disk delivering 1.05 GB through three platters or five recording surfaces. This drive was utilized within IBM’s 9336 Disk Unit and the 9337 Disk Array systems.

Floppy disk drive

IBM was a pioneer in floppy disk technology, debuting the first 8-inch floppy disk drive in 1971 as a read-only medium for program loading, followed by its initial read/write version in 1973 with the launch of the 3740 Data Entry System. While IBM established early standards for 8-inch floppy drives, it never marketed these drives independently, thereby allowing broader industry development to proceed without restriction.

At one stage, IBM represented the largest OEM buyer of 5-inch floppy drives, and its adoption of the dual-sided, 48 tracks-per-inch variant helped cement this format as an industry benchmark. Although IBM had plans to produce these drives along with smaller sizes, all such manufacturing efforts were discontinued by 1985. Notably, IBM’s attempt to OEM a 4-inch DemiDiskette in 1983 did not succeed.

"Star" series of HDDs

On October 17, 1994, IBM’s Storage Systems division introduced three distinct families of hard disk drives: the Travelstar line featuring 2-inch drives aimed at notebook computers; the Deskstar series with 3-inch drives designed for desktop use; and the Ultrastar range of 3-inch drives intended for high-performance applications.

Comparing IBM’s first HDD with its final models

The following table contrasts IBM’s inaugural HDD, the RAMAC 350, against its last three "Star" series OEM hard drives, illustrating remarkable advancements in cost efficiency, size reduction, storage capacity, and overall performance over a span of nearly five decades.

Parameter (units) RAMAC 350 Ultrastar 146Z10 Deskstar 180GXP Travelstar 80GN Maximum improvement over 46 years
Release date Sep 1956 Jul 2002 Oct 2002 Nov 2002
Storage capacity (GB) 0.004 146 180 80 48,000 times
Physical dimensions (inches) 60×68×29 4×1×5.75 4×1×5.75 2.75×0.38×3.95
Physical dimensions (mm) 1500×1700×700 102×25×146 102×25×146 70×9.5×100
Volume (cubic inches) 118,320 23 23 4 29,161 times
Volume (liters) 1,939 0.4 0.4 0.1
Weight (pounds) 2,140 1.7 1.4 0.2 1,244 times lighter
Weight (kilograms) 971 0.8 0.64 0.095
Power consumption (watts) Approx. 2374 watts (8100 BTUs/hour), up to 5500 VA depending on model 16 10.3 1.85 1,283 times more efficient
Power efficiency (megabytes per watt) 0.0016 9,125 17,476 43,243 27 million times improvement
Retail price (Template:US$) \$34,500 (\$234,000 adjusted to 2002 dollars) \$1,200 \$360 \$420
Cost per megabyte (Template:US$) \$9,200 (\$68,000 adjusted to 2002 dollars) \$0.0082 \$0.0020 \$0.0053
Areal density (megabits/in²) 0.002 26,263 46,300 70,000
Areal density (kilobits/mm²) 0.003 40,708 '71,765 '108,500
' Volume density (GB/in³) '0.00000003 '6 '8 '20
' Volume density (MB/cm³) '0.000002 '388 '478 '1,203
' Average latency (ms) '25 '3 '4 '7
' Average seek time (ms) '600 '5.9 '10.2 '12
' Data transfer rate (MB/s) '0.001 '103 '29.4 '43.75


DASD Devices Beyond HDDs and FDDs

In certain IBM operating systems, both hard disk drives (HDDs) and floppy disk drives (FDDs) fall under the category of DASDs (direct access storage devices). Additional technologies classified as DASDs include:

IBM 7320 Drum

Released in 1962, the IBM 7320 is a storage unit based on magnetic drum technology.

IBM 2301 Drum

The IBM 2301, introduced in the late 1960s, is a magnetic drum storage apparatus.

IBM 2303 Drum

Dating back to 1964, the IBM 2303 is another example of a magnetic drum storage device.

IBM 2321 Data Cell

Unveiled in 1964, the IBM 2321 Data Cell employs short strips of magnetic tape for data storage. It accommodates ten removable cells, each with a capacity of 40 MB, resulting in an aggregate of 400 MB.

IBM 3850 Mass Storage System

The IBM 3850 Mass Storage System, launched in 1974, is a tape cartridge library that stages data onto IBM 3330 or 3350 disk drives. This system offers virtual disk drives to the operating environment.

See also

External links

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