IBM 355

IBM

Company type	Public
Industry	Computer hardware, data storage
Founded	June 16, 1911 (1911-06-16) in Endicott, New York, United States
Headquarters	Armonk, New York , United States
Products	Magnetic disk storage devices (hard disk drives, floppy disk drives)
Number of employees	350,000 (2023)
Website	www.ibm.com

IBM was a pioneer in producing magnetic disk storage devices from 1956 until 2003, at which point it divested its hard disk drive division to Hitachi. IBM’s workforce was instrumental in the creation of both the hard disk drive (HDD) and the floppy disk drive (FDD), contributing numerous technological advancements. The core mechanical architecture of hard disk drives has largely remained unchanged since the introduction of the IBM 1301, with performance benchmarks adhering to consistent standards established in the 1950s. Over the decades, these storage solutions saw dramatic decreases in both cost and physical size, while simultaneously achieving substantial improvements in capacity and speed.

From 1969 through the mid-1980s, IBM manufactured 8-inch floppy disk drives but did not become a leading producer of the smaller 5.25- or 3.5-inch variants. Although IBM consistently marketed its magnetic disk drives, it only began providing them under original equipment manufacturer (OEM) agreements starting in 1981. By 1996, IBM had discontinued producing HDDs exclusively for its own systems and shifted entirely to offering all models as OEM products.

IBM has employed multiple designations for its magnetic disk drives, such as direct-access storage device (DASD), disk file, and diskette file. For clarity and alignment with industry terminology, this article refers to these devices as 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 launched by IBM on September 14, 1956, as an integral component of the IBM 305 RAMAC system. A comparable model, the IBM 355, was introduced for use with the IBM 650 RAMAC system. The initial prototype was delivered to Zellerbach Paper Company in San Francisco in June 1956, with commercial shipments commencing in November 1957 to customers including United Airlines.

Created to facilitate real-time business accounting tasks, the IBM 350 stored five million 6-bit characters (equivalent to 3.75 MB) across fifty-two disks measuring 24 inches each, utilizing a total of 100 recording surfaces. The disks rotated at a speed of 1200 revolutions per minute, enabling a data transfer rate of 8,800 characters per second. A mechanical selection mechanism managed access to specific disk pairs and tracks. Several enhanced versions were developed during the late 1950s. The RAMAC 305 system paired with the IBM 350 was leased at a rate of $3,200 monthly. Production of the IBM 350 ceased in 1969.

The patent US3503060 stemming from the RAMAC project is regarded as a seminal invention in disk drive technology. Although IBM's Board initially canceled the project due to concerns about its impact on punch card operations, development persisted at IBM San Jose until receiving endorsement from IBM’s president.

Physically, the unit measured roughly 60 inches in length, stood 68 inches tall, and was 29 inches wide, weighing approximately one ton—requiring forklifts or cargo aircraft for transportation. According to Hitachi Global Storage Technologies’ research vice president, marketing considerations limited capacity expansion despite technical feasibility; nevertheless, double-capacity models were introduced in 1959.

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 initiative commenced in 2002 under Al Hoagland’s leadership alongside Santa Clara University and later moved in 2005 to the Computer History Museum located in Mountain View, California, where it remains on public display.

IBM 353

The IBM 353, implemented on the IBM 7030, bore resemblance to the IBM 1301 but offered an enhanced transfer speed. It provided storage for 2,097,152 (2²¹) words of 64 bits each (totaling 134,217,728 bits) and achieved a data transfer rate of 125,000 words per second. A prototype delivered in late 1960 was notable as the first disk drive to utilize a dedicated head per surface that hovered on compressed air, continuing the approach pioneered by the earlier IBM 350. Production versions adopted self-flying heads similar to those found in the IBM 1301.

IBM 355

Unveiled on September 14, 1956, the IBM 355 was designed to complement the widely used IBM 650. It incorporated the IBM 350 disk mechanism but featured up to three access arms instead of just one as in the IBM 350. The unit stored six million decimal digits alongside 600,000 sign characters. Data transfer involved moving entire tracks between the disk and the magnetic core memory of the 653—an optional IBM 650 component with sixty signed ten-digit words, sufficient to hold a single disk track or tape record—plus two additional unrelated functionalities.

IBM 1405

Launched in 1961 for the IBM 1400 series business computers, the IBM 1405 Disk Storage Unit was available in two configurations. Model 1 could store ten million alphanumeric characters (equivalent to sixty million bits) across twenty-five disks; Model 2 doubled this capacity with twenty million characters (one hundred twenty million bits) on fifty disks. The disks were arranged vertically and rotated at a speed of 1200 rpm.

Each disk surface contained two hundred tracks divided into five sectors; sectors numbered zero through four were positioned on the top side, while sectors five through nine were on the bottom. Each sector held between one hundred seventy-eight and two hundred characters. There were one to three forked access arms, each equipped with two read/write heads (one for the top and one for the bottom), which moved vertically to select among disks zero through forty-nine and horizontally to locate tracks zero through one hundred ninety-nine. Each track provided ten sectors, with read/write operations taking approximately ten milliseconds per sector.

Access times varied from a minimum of one hundred milliseconds up to a maximum of seven hundred milliseconds for Model 1 and eight hundred milliseconds for Model 2. Model 2 contained one hundred thousand sectors capable of holding either two hundred characters in move mode or one hundred seventy-eight characters in load mode, which included an additional word mark bit per character. Model 1 comprised fifty thousand sectors.

IBM 7300

The IBM 7300 Disk Storage Unit was engineered for use with the IBM 7070, with a second model announced in 1959. Nonetheless, following the introduction of the IBM 1301 on June 5, 1961, customers utilizing the IBM 7070 and IBM 7074 favored the IBM 1301 over the IBM 7300. The technology underlying the IBM 7300 shared components and design elements with earlier models such as the IBM 350, IBM 355, and IBM 1405.

IBM 1301

Introduced on June 2, 1961, the IBM 1301 Disk Storage Unit targeted users of mainframe computers from the 7000 series as well as the IBM 1410. Each module stored twenty-eight million characters (twenty-five million when used with the IBM 1410), comprising twenty-five substantial disks with forty user-accessible recording surfaces containing two hundred fifty tracks each. The Model 1 configuration consisted of a single module; Model 2 stacked two modules vertically. Disks spun at eighteen hundred revolutions per minute, delivering data at a rate of ninety thousand characters per second.

A significant advancement was its architecture featuring an individual arm and read/write head assigned to each surface, all moving simultaneously like a comb. This eliminated delays caused by repositioning heads between disks and reduced maximum access time to one hundred eighty milliseconds. The IBM 1301 also pioneered aerodynamically shaped heads that fly on a thin cushion of air above disk surfaces, allowing closer proximity and enhanced performance.

Connectivity was established through the IBM 7631 File Control unit, enabling compatibility with either an IBM 1410 or a IBM 7000 series system, or permitting shared access between two machines.

The pricing strategy positioned the IBM 1301 as a high-end storage solution: Model 1 leased at $2,100 per month or purchased for $115,500; Model 2 leased at $3,500 per month or sold for $185,000. The IBM 7631 controller cost an additional $1,185 monthly lease or $56,000 to buy. All versions were discontinued by 1970.

IBM 1302

Launched in September 1963, the IBM 1302 Disk Storage Unit offered a fourfold increase in capacity compared to the 1301, reaching 117 million 6-bit characters per module. It delivered an average access time of 165 milliseconds and supported a data transfer rate of 180,000 characters per second, which was more than twice as fast as its predecessor. Each module incorporated two separate access mechanisms designed for the inner and outer cylinders. The Model 2 configuration stacked two modules together, effectively doubling the storage capacity. Leasing fees were set at $5,600 per month for Model 1 and $7,900 per month for Model 2, with purchase prices of $252,000 and $355,500 respectively. The IBM 7631 controller added an additional cost of $1,185 monthly or $56,000 if purchased outright. Production of the 1302 ceased in February 1965.

IBM 1311

Announced on October 11, 1962, the IBM 1311 Disk Storage Drive was designed to serve medium-sized business and scientific computing environments. It utilized removable IBM 1316 disk packs capable of storing two million characters each. Throughout the 1960s, seven variants were released before being phased out by the early 1970s.

Each IBM 1316 Disk Pack measures about four inches in height and weighs approximately ten pounds. The pack contains six disks measuring fourteen inches in diameter with ten recording surfaces in total. Operating at 1500 revolutions per minute, each surface includes 100 tracks divided into twenty sectors, with each sector holding one hundred characters. The read/write heads move hydraulically across the tracks. Encased in a protective plastic shell, the disk pack is inserted and removed using a locking handle mechanism—a feature that influenced future removable storage designs.

The seven IBM 1311 models included:

1. Master drive for IBM 1440/1460/1240 systems managing up to four Model 2 drives (1962–1971).
2. Slave drive compatible with master capabilities (1962–1975).
3. Master drive for IBM 1620/1710 systems controlling up to three Model 2 drives without special features (1962–1971).
4. Master drive for IBM 1401 systems managing up to four Model 2 drives (1962–1971).
5. Master drive for IBM 1410/7010/7740 systems featuring standard Direct Seek and controlling up to four Model 2 drives (1963–1971).
6. Presumed master drive introduced in 1968 and withdrawn in 1971.
7. Presumed slave drive introduced in 1968 and withdrawn in 1971.

Available optional features comprised:

• Direct Seek: Removes the need to return to zero before seeking.
• Scan Disk: Facilitates fast automatic data searching.
• Seek Overlap: Permits overlapping seek operations when multiple drives are active.
• Track Record: Enhances capacity by recording one large record per track instead of multiple sectors, increasing total storage to roughly 17.9 million bits in six-bit mode and over 18.7 million bits using seven-bit encoding.

Master models (numbers 1,3,4,5) contained extra power supplies and control circuitry, making them approximately one foot wider than the Model 2 slave versions.

IBM 2302

The IBM 2302 represents the System/360 adaptation of the 1302, with track formatting tailored to align with S/360 DASD standards rather than those of the earlier 7000 series.

It employs a fixed module housing twenty-five platters with forty-six recording surfaces. The Model 3 includes a single module; Model 4 incorporates two modules. Each module features two independent access mechanisms—referred to as access groups—one dedicated to the innermost 250 cylinders and another serving the outermost 250 cylinders. Each access mechanism provides one read/write head per track. The average rotational latency is seventeen milliseconds, with a maximum of thirty-four milliseconds; maximum seek time per access group is up to one hundred eighty milliseconds. Each track contains approximately 4,985 bytes; formatted capacity per module reaches about one hundred twelve megabytes. Connectivity to IBM mainframes is facilitated through the IBM 2841 Storage Control Unit.

IBM 2305

Introduced in 1970, the IBM 2305 fixed-head storage device and the IBM 2835 Storage Control initially interfaced with the 360/85 and 360/195 systems through the IBM 2880 Block Multiplexor Channel.

The 2305 gained significant popularity within System/370's Virtual Storage environment, frequently utilized as a paging device on models such as the 3155, 3165, and 3081 (the latter requiring specialized microcode). It was also well-suited for managing small, high-transaction data sets like catalogs and job queues.

The 2305-1 variant provides a storage capacity of 5.4 MB and achieves a data transfer rate of 3.0 MB/s via a 2-byte channel interface, with an average access time of approximately 2.5 milliseconds. Meanwhile, the larger 2305-2 model offers an 11.2 MB capacity, operates at a transfer speed of 1.5 MB/s, and has an average seek time of around 5 milliseconds.

Engineered to deliver rapid and continuous access to modest-sized data volumes, the 2305's combination of capacity and speed made it particularly effective for system-resident functions, work files, job queues, indices, and frequently accessed datasets. Its swift response times rendered it especially effective as a paging device in systems handling transaction rates exceeding 1.5 per second.

IBM 2311

The IBM 2311 Disk Storage Drive debuted in 1964 alongside the 2841 Control Unit, supporting the IBM System/360 series as well as compatibility with the IBM 1130 and IBM 1800. It also connected directly to the IBM System/360 Model 20 and Model 25 systems. All units employed removable IBM 1316 Disk Packs, originally designed for use with the IBM 1311.

The Model 1 connects to most IBM mainframes via the 2841 Control Unit; for the System/360 Model 25, a Disk Attachment Control provides equivalent functionality. Disk packs utilize IBM's count key data variable-length record format. Conversely, Models 11 and 12—designed for the System/360 Model 20's integrated control unit—use a fixed-sector format; disk packs are not interchangeable between these models and Model 1 drives.

Mechanically resembling the IBM 1311 but featuring advanced recording technology, the IBM 2311 stores up to 7.25 megabytes on a six-platter removable disk pack. It contains ten read/write heads mounted on a hydraulically actuated mechanism that accurately positions heads over each track. Each disk surface holds 200 tracks plus three spare tracks reserved for defect management. The average seek time is approximately 85 milliseconds, with a data transfer rate of about 156 kB/s.

A standardized electrical interface across System/360 models enabled third-party vendors to manufacture plug compatible disk drives, encouraging competition within the IBM-compatible storage market.

IBM 2314 Disk Access Storage Facility Model 1

Released in April 1965, the IBM 2314 Disk Access Storage Facility Model 1 supported both System/360 and System/370 platforms and incorporated a Two Channel Switch allowing simultaneous connections to two channels. While its disk mechanism was similar to that of the IBM 2311, it featured substantially enhanced recording density.

This device stored over 29 million characters on an IBM 2316 removable disk pack that increased platter count from six to eleven, providing twenty recording surfaces in total. The drive employed twenty read/write heads mounted on a hydraulically actuated mechanism with mechanical detents for precise track positioning. Initial access times were comparable to those of the IBM 2311; however, subsequent improvements lowered latency while doubling data transfer rates to approximately 310 kB/s.

The original Model 1 configuration consisted of nine drives sold collectively as one unit, along with a storage control unit, one single-drive module, and two four-drive modules. Drives were installed in pull-out drawers—colloquially referred to as "Pizza Ovens"—which facilitated straightforward disk pack handling. Although only eight drives could be accessed concurrently, the ninth served as an offline spare allowing maintenance without interrupting operations. Each drive’s system address was configured using user-swappable plugs to permit flexible reconfiguration.

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

Subsequent models of the IBM 2314 were introduced later:

IBM 2314 Direct Access Storage Family - Variants

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

• The 2312 Disk Storage, featuring a single-drive unit.
• The 2313 Disk Storage, comprising four drives.
• The 2318 Disk Storage, equipped with two drives.

IBM 2319

To compete against plug-compatible manufacturers offering alternatives to the 2314 storage, IBM launched the affordable three-drive 2319 module in 1970. This model was derived by removing one drive from the four-drive 2313 and reintroducing it as the 2319 A1, which was leased at a significantly lower rate. This approach reduced expenses for new clients while maintaining existing rental rates for current users. The 2319-A1 interfaces with integrated controllers designed for System/370 Models 135 and 145. Additionally, traditional 2314 DASD units such as the 2312 or 2318 can be connected to the 2319-A1. The 2319 B series supports configurations of three, six, or nine drives linked to a new 2314 Model B Storage Control Unit.

IBM 3310

Released on January 30, 1979, the IBM 3310 Direct Access Storage Device was developed specifically for IBM 4331 midrange computer systems. Each drive provided a storage capacity of 64.5 MB. Utilizing fixed-block architecture, the 3310 was compatible with DOS/VSE and VM, which were the only S/370 operating systems supporting FBA devices.

IBM 3330

The IBM 3330 Direct Access Storage Facility, codenamed Merlin, was introduced in June 1970 for use with IBM System/370 and System/360/195 systems. Initial offerings consisted of a two-drive Model 1 and a single-drive Model 2. Each removable disk pack stored 100 MB, featured an access time of 30 ms, and achieved data transfer rates of up to 806 kB/s. A significant advancement was the incorporation of built-in error correction utilizing fire codes capable of correcting error bursts up to eleven bits, thereby improving reliability while lowering costs.

The standard setup included one storage control unit (3830 Model 1) physically attached to a single 3330 drive, with support for adding up to three more drives in a chain for a maximum of eight drives per string. In August 1972, IBM introduced the 3830 Model 2 Storage Control along with the 3333 Disk Storage and Control, which separated control units from disk drives. The upgraded 3830 acted as a director-style controller managing multiple strings; each lead unit in a string (the 3333) combined a controller with two drives and could manage up to three additional attached 3330 drives (up to eight drives per string). The Model 2 controller could connect two such strings (allowing up to sixteen drives), with optional string switches enabling dual-controller connections.

In 1973, IBM announced double-density (-11) variants: the 3333–11, the 3330-11, and larger-capacity (200 MB) disk packs labeled as the 3336–11. Mixing single-density and double-density drives within the same string was unsupported. Upgrading from the original models to Model-11 versions was feasible but complicated, requiring drive conversion and full data transfer.

The IBM 3330 series was discontinued in 1983.

IBM 3340 and IBM 3344

Although sharing many characteristics, only the IBM 3340 functions as the lead unit in a string; there are no A model versions of the IBM 3344, which must be connected to an IBM 3340 A model serving as head of string.

IBM 3340

The IBM 3340 Direct Access Storage Facility, known by its codename Winchester, was introduced in March 1973 for the IBM System/370. It came in three variants: the 3340-A2 featuring two drives and a controller, as well as the B2 and B1 models with two and one drive(s) respectively. Up to eight B-units could be connected to a single A2 controller.

This system utilized removable data modules that housed both the head and arm assembly; the module’s access door opened mechanically during loading and unloading, removing the need to detach covers as was common with earlier disk packs. It delivered an average access time of 25 milliseconds and supported data transfer rates of 885 kB/s. IBM marketed three types of 3348 Data Modules: one with a 35 MB capacity and two with 70 MB, one of which incorporated 500 KB fixed heads for faster access. The 3340 included error correction capabilities and was phased out in 1984.

Developed at IBM’s San Jose facility under Ken Haughton’s leadership, the original concept involved two removable 30 MB modules—hence the Winchester nickname, inspired by the Winchester .30-30 rifle. Although storage capacities grew over time, this code name remained in use.

A significant breakthrough was the introduction of a low-cost head design that permitted the heads to land directly on and lift off from the spinning disk surface without unloading. This innovation, known as "Winchester technology," simplified and reduced the cost of the head and arm mechanism, eventually becoming an industry benchmark. The terms Winchester or Winnie were commonly used to describe hard drives through the early 1990s but have since fallen out of regular use.

IBM 3344

The IBM 3344 shared similarities with the 3340 but differed by employing fixed media rather than removable 3348 data modules. Each spindle supported four logical drives, each matching the capacity of a 3348–70 module. Available exclusively in dual-drive configurations, it did not include an A (head of string) model. The 3344-B2F variant featured fixed heads across certain cylinders on both drives. Both the 3344-B2 and 3344-B2F required connection to a 3340-A2 or 3340-A2F unit serving as head of string. Internally, the IBM 3344 was identical to the IBM 3350; distinctions were confined to differences in microcode within their control units.

IBM 3350

Introduced in 1975 for IBM System/370 platforms, the IBM 3350 Direct Access Storage Facility carried the codename Madrid. It featured sealed head-disk assemblies (HDAs) with integrated head and arm components, establishing a design standard for subsequent IBM DASD products. Each HDA contained 555 cylinders, utilized 30 heads, and stored approximately 19,069 bytes per track, resulting in roughly 317 MB total capacity.

Available models included A2, A2F, B2, B2F, C2, and C2F configurations, each comprising two HDAs. The A2 and A2F models incorporated an additional electronics board that allowed connection to storage control units—commonly referred to as controllers or head-of-string units. Typical setups paired one A2 or A2F unit with up to three B2 units or combined two B2s with a C2 unit. Generally, the A2 contained a string switch enabling dual connections to storage control units such as the IBM 3830 Model 2 or Integrated Storage Control within CPUs like the IBM 3148. Later controllers like the IBM 3880 maintained backward compatibility with these arrangements.

The C2 model included a controller that acted as a secondary path for itself and other units but primarily served as a backup should the A unit’s controller fail. Valid strings for IBM 3350 systems included configurations such as -A, -AB, -ABB, -ABBB, -AC-, -ABC-, and -ABBC-.

Models designated with “x2F” (for example, A2F) incorporated fixed-head regions spanning the first five cylinders on both HDAs. This design effectively eliminated seek time for these cylinders by keeping heads stationary over frequently accessed areas. This feature was optimized for high-use data like HASP or JES checkpoint files on spool devices to enhance performance by minimizing head movement. Additionally, it supported TSO swap data and system swap data within OS/360 successors (MVT, SVS) and MVS operating environments, thereby improving efficiency during user or batch job context switches.

The IBM 3350 product line was retired in September 1994.

IBM 3370

In January 1979, IBM introduced the IBM 3370 Direct Access Storage Device tailored for 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 pioneer hard disk drive to implement thin-film head technology, developed at the Thomas J. Watson Research Center. The 3370 utilized a fixed-block architecture and was compatible with DOS/VSE and VM operating environments.

IBM 3375

The IBM 3375 served as a complementary model featuring count key data architecture, designed to operate with OS/360 and its subsequent versions.

IBM 3380

Debuting on June 11, 1980, the IBM 3380 incorporated thin-film head technology and provided a total capacity of 2.52 GB per unit, achieved through two hard disk assemblies each equipped with two independent actuators accessing 630 MB. It supported a data transfer speed of 3 MB/s and had an average access latency of 16 milliseconds. Initial pricing ranged between $81,000 and $142,200. Due to challenges related to tribology between the heads and media surfaces, shipments commenced in October 1981.

The typical setup consisted of one A unit paired with up to three B units; each IBM 3380 housed four devices, enabling up to sixteen devices per string. Usually connected via two paths to a 3880 storage control unit, the system allowed two concurrent I/O operations targeting distinct HDAs.

In February 1985, IBM launched the double-density Extended Capability Model (3380 E), doubling capacity to 5.04 GB per unit by featuring two actuators of 1.26 GB each across two assemblies. Later, in August 1987, the triple-capacity Model K was introduced, offering 7.562 GB per unit with two actuators at 1.89 GB each. Both Models J and K supported four-path connectivity, facilitating up to thirty-two devices through a 3990 storage control unit and enabling four simultaneous I/O processes.

The IBM 3380 series comprised twelve variants: six A-units (which combined string heads with controller logic), five B-units (designed for connection to A or C units), and one C-unit (featuring direct channel attachment). Production of the final models ceased in May 1996 after an exceptionally long lifespan exceeding fifteen years—an uncommon duration for disk drive technology.

IBM 3390

Launched in November 1989, the IBM 3390 Direct Access Storage Device family provided capacities up to 22 gigabytes distributed across multiple drives. Depending on configuration and size, system prices varied from $90,000 to $795,000.

A typical IBM 3390 string includes a central A unit containing four or eight devices, optionally accompanied by one or two B units that can hold up to twelve devices each. Operating in four-path mode, the system connects to a 3990 storage control unit capable of supporting an additional 3390 string—allowing up to sixty-four devices within a single subsystem.

Each Hard Disk Assembly (HDA) houses two actuator-head units along with platters: Model 1 offers a capacity of 1.89 GB per HDA; Model 2 doubles this to 3.78 GB per HDA. The Model 3 update released in 1991 increased capacity further to 5.67 GB per HDA, while the Model 9 introduced in 1993 expanded it to an impressive 11.3 GB per HDA.

Unlike prior DASD models that employed large AC motors driving belts externally, the IBM 3390 HDAs utilize directly driven DC motors enclosed within the assembly.

The Model 9 marked IBM’s final iteration of Single Large Expensive Disk (SLED) drives.

IBM 9345

Introduced in November 1990 as a Request Price Quotation (RPQ) for IBM’s SuperComputing Systems Extensions (SCSE), the IBM 9345 was developed at IBM’s San Jose facility under the project name Sawmill. This full-height 5¼-inch hard disk drive supported up to eight 130 mm platters, delivering a maximum storage capacity of 1.5 GB. It was distinguished as the first HDD to incorporate Magnetoresistive (MR) head technology.

IBM 9340

In October 1991, IBM launched the 9345 DASD within the 9340 family of channel-attached count key data (CKD) DASD subsystems designed for IBM mainframes, including the ES/9000 series processors. The Model 1 of the 9345 housed two 1.0 GB HDDs, whereas Model 2 contained two drives each with 1.5 GB capacity.

From an operational standpoint, the 9340/9345 shared similarities with the 3990/3390 series; however, it lacked the non-volatile RAM cache found in the 3990 and supported a shorter maximum block length than the 3390.

The OS Input/Output Supervisor (IOS) utilized a specialized initializer named IECCINIT to identify device attributes during startup, recognizing that the 9340 did not include non-volatile cache and that the 9345 had diminished track capacity. Consequently, these devices were assigned distinct device types compared to the 3990/3390 series.

9330 family of disk drives

1. The 9331 Diskette Unit models 1 and 11 incorporated a single 8-inch floppy disk drive; models 2 and 12 contained one 5-inch floppy disk drive.
2. The 9332 Direct Access Storage Device employed the IBM 0667 hard disk drive.
3. The 9333 High Performance Disk Drive Subsystem utilized either IBM 0664 or IBM 0681 hard drives depending on the specific model.
4. The 9334 Disk Expansion Unit connected between one and four SCSI hard drives to RS/6000 platforms.
5. The 9335 Direct Access Storage Subsystem featured IBM’s proprietary "Kestrel" hard drive with an 850 MB capacity, consisting of three 14-inch platters and dual rotary actuators accessing multiple surfaces; it was designed for rack mounting and debuted alongside the IBM 9370 Information System in October 1986. No original equipment manufacturer (OEM) variant was produced.
6. The IBM 0681 hard drive powered the 9336 Disk Unit (also known as Redwing).
7. The IBM 0662 (Spitfire) or IBM 0663 (Corsair) hard drives were used in the 9337 Disk Array Subsystem.

IBM 2310

The IBM 2310 Removable Cartridge Drive appeared in 1964 alongside the IBM 1800 system and was incorporated into the IBM 1130 in 1965, most likely shipping initially with the latter in late that year. It stored a total of 512,000 sixteen-bit words (equivalent to 1,024,000 bytes) on an IBM 2315 cartridge. This cartridge housed a single oxide-coated aluminum platter encased within a plastic shell featuring openings for both the read/write arm and two heads.

IBM 5444

Released in September of 1969 as part of System/3 and developed at IBM’s Hursley laboratory in England under the codename Dolphin, the IBM 5444 utilized a disk cartridge labeled as the IBM 5440 containing one fourteen-inch platter. It was available in three configurations:

• Model 1: featured one fixed disk plus one removable disk, each having one hundred tracks per surface; cartridge capacity reached approximately 1.23 MB
• Model 2: included one fixed and one removable disk, each with two hundred tracks per surface; cartridge capacity doubled to about 2.46 MB
• Model 3: contained only one removable disk with two hundred tracks per surface; cartridge capacity also around 2.46 MB

IBM 62GV

First shipped in May of 1974, the IBM 62GV was engineered at IBM’s Hursley lab under the project name Gulliver and initially offered a five megabyte storage capacity. Subsequent models included the higher-capacity versions: the IBM 62TM at ten megabytes and another model with fourteen megabytes. Its mechanical design incorporated a Swinging Arm actuator paired with a single fourteen-inch platter. This actuator mechanism became IBM's most widely licensed electromechanical innovation, eventually becoming an industry standard across hard disk drives throughout the eighties and remaining in use nearly forty years later. Approximately one hundred seventy-seven thousand units of the IBM 62GV were shipped, marking it as the first HDD to surpass sales of one hundred thousand units.

OEM and Small Systems Hard Drives

This segment details IBM-produced hard disk drives marketed as OEM components and designed for IBM small-scale systems such as the System/3, System/32, /34, /36, and AS/400. Drives are categorized by their OEM model numbers and arranged according to their initial shipment dates.

IBM 0680

Introduced in 1979, the 0680 was deployed across numerous IBM small systems and entry-level System/370 variants as the 3310 direct access storage device. Officially announced in September 1981 as the 0680 OEM model, it was engineered at IBM’s Hursley laboratory in the United Kingdom under the project name Piccolo. This unit incorporated six 8-inch (210 mm) platters, offering a starting capacity of up to 65MB alongside an enhanced rotary actuator mechanism.

A higher-capacity variant, designated 62SW, became available in June 1984 but experienced modest market adoption due to its cost per megabyte being comparable to that of the 62GV.

IBM 0676

The 0676 made its debut in November 1982 as a 5247 Disk Storage Unit tailored for the IBM System/23 Datamaster. Developed at IBM Rochester, Minnesota under the internal code 21ED, this 8-inch hard drive provided storage options of either 15 or 30 MB through configurations of two or four 210 mm platters. In 1983, it was incorporated into the S/36’s 5360 System Unit. By 1984, its storage capacity doubled by increasing the number of tracks per surface and was subsequently included in the S/36’s upgraded 5362 System Unit.

IBM 0665

Released in October 1985 within the PC AT (5170) chassis, the 0665 was created under the codename "Pixie" at IBM Rochester. This model featured a 5-inch form factor with storage capacities ranging from 20 to 44 MB.

IBM 0667

The 0667 arrived in August 1986. Developed at IBM Rochester and codenamed "Grant," it was a full-height ESDI hard drive containing up to four 130 mm platters and providing a maximum capacity of 70 MB. This drive was offered as an optional component for certain PC RT models (6150, 6151, 6152) as well as System/36 Model System Units (5363, 5364).

IBM 0669

Shipping in 1987, the 0669 originated from IBM Rochester under the project name "Grant-Prime." It was a full-height, five-inch HDD featuring four 130 mm platters with a maximum capacity of up to 115 MB. This drive served as the internal storage solution for both the System/36 Model 5363 and Series 1 Model 4956 System Units.

IBM 0671

Also introduced in 1987, the 0671 was developed at IBM Rochester under the codename "Lee." This full-height ESDI five-inch hard drive supported up to eight 130 mm platters with a total capacity reaching as high as 316 MB. Notably, it marked IBM’s initial implementation of thin metal film recording surfaces. The drive was integrated into the AS/400 system’s 9404 System Unit in 1988, accommodating configurations of two or three drives per unit.

IBM 0661

The 0661 appeared in 1989 branded as model 371. Jointly developed by IBM Rochester and Hursley labs under the codename "Lightning," it was a SCSI hard disk offering up to 320 MB storage using eight disks measuring approximately 95 mm with fourteen heads. A subsequent "Turbo" variant with a capacity of 400 MB was released in 1990. This model became a standard option across prominent IBM platforms such as the AS/400 System Unit Model CXX.

IBM 0681

Introduced in April of 1990 from IBM’s Hursley laboratory and known internally as Redwing—the final HDD project from that site—this full-height five-inch drive supported up to twelve platters sized at 130 mm each for a maximum capacity of approximately 857 MB. It was also IBM’s first HDD utilizing PRML data decoding technology. The drive powered the launch of the 9333 Disk Drive Subsystem in early 1992, which later featured an upgraded version with increased density delivering up to about 1.07 GB.

IBM 0663

The 0663, introduced in late 1991 and developed under the codename "Corsair," was a compact 3-inch hard disk drive with a half-height (1.6-inch) profile. It delivered up to 1 GB capacity using eight 95 mm platters. This model appeared in select PS/2 and RS/6000 systems and marked IBM's inaugural use of Magnetoresistance (MR) heads in an OEM disk drive.

IBM 0664

Released in November 1992, the 0664—created at IBM Rochester, Minnesota, under the project name "Allicat"—was a full-height 5-inch hard drive (measuring 3.25 inches tall). It combined two 3-inch drives into a single unit, providing as much as 2.013 GB storage across up to eight 95 mm platters.

IBM 0662

The 0662, launched in June 1993 and developed as "Spitfire" also at IBM Rochester, was a full-height (1-inch tall) hard disk with a 3-inch form factor. It offered a capacity of 1.05 GB distributed over three disks or five recording surfaces. This drive was utilized internally within the 9336 Disk Unit and the 9337 Disk Array.

Floppy disk drive

IBM was a pioneer in floppy disk technology, debuting the 8-inch floppy disk drive in 1971 primarily as a read-only program loader, followed by its first read/write model in 1973 incorporated into the 3740 Data Entry System. Although IBM established foundational standards for the 8" floppy drives, it chose not to market these drives independently, which allowed the broader industry to develop without direct IBM influence.

At one point, IBM stood as the largest OEM buyer of 5-inch floppy drives, favoring two-sided units with 48 tracks per inch that eventually became industry benchmarks. Despite having plans to manufacture these and smaller formats internally, IBM abandoned such production efforts by 1985. Additionally, its attempt in 1983 to OEM the smaller 4-inch DemiDiskette did not succeed.

"Star" series of HDDs

On October 17, 1994, IBM's Storage Systems division unveiled three distinct families of hard drives: the Travelstar series featuring compact 2-inch drives designed for laptops; the Deskstar line consisting of 3-inch drives aimed at desktop computers; and the Ultrastar models, also with a 3-inch form factor but tailored for high-performance computing environments.

IBM's first HDD compared to its latest models

The following table contrasts IBM’s original hard disk drive, the RAMAC 350, with the last three HDD models from its "Star" series of OEM products. The comparison illustrates vast improvements in cost efficiency and miniaturization alongside remarkable advancements in storage capacity and operational performance.

Parameter (units)	RAMAC 350	Ultrastar 146Z10	Deskstar 180GXP	Travelstar 80GN	Improvement over 46 years (maximum)
Announced	Sep 1956	Jul 2002	Oct 2002	Nov 2002
Capacity (gigabytes)	0.004	146	180	80	48,000
Dimensions (inches)	60×68×29	4×1×5.75	4×1×5.75	2.75×0.38×3.95
Dimensions (mm)	1500×1700×700	102×25×146	102×25×146	70×9.5×100
Volume (in³)	118,320	23	23	4	29,161
Volume (litres)	1,939	0.4	0.4	0.1
Weight (lbs)	2,140	1.7	1.4	0.2	1,244
Weight (kg)	971	0.8	0.64	0.095
Power consumption (watts)	8100 BTUs/hour (2374 watts), up to 5500 VA depending on model	16	10.3	1.85	1,283
Power efficiency (megabytes/watt)	0.0016	9,125	17,476	43,243	27,375,856
List price (Template:US$)	$34,500 ($234,000 in equivalent value for 2002)	$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
Volumetric density (gigabytes/in³)	0.00000003	6	8	20
Volumetric density (megabytes/cm³)	0.000002	388	478	1,203
Rotational latency (ms)	25	3	4	7
Average seek time (ms)	600	5.9	10.2	12
Data transfer rate (megabytes/s)	0.001	103	29.4	43.75

DASD Devices Beyond HDDs and FDDs

In certain IBM operating systems, both HDDs and FDDs are categorized as DASDs (direct access storage devices). Additional DASD technologies encompass:

IBM 7320 Drum

The IBM 7320 represents a magnetic drum storage unit that was first introduced in 1962.

IBM 2301 Drum

Released in the late 1960s, the IBM 2301 is a magnetic drum-based storage device.

IBM 2303 Drum

Debuting in 1964, the IBM 2303 is another example of a magnetic drum storage apparatus.

IBM 2321 Data Cell

Announced in 1964, the IBM 2321 Data Cell utilized short magnetic tape strips for data retention. It featured ten removable cells, each with a capacity of 40 MB, resulting in a total of 400 MB.

IBM 3850 Mass Storage System

The IBM 3850 Mass Storage System, introduced in 1974, functioned as a tape cartridge library system that staged data onto IBM 3330 or 3350 disk drives and emulated virtual disk drives for the host system.

See also

• History of the floppy disk
• History of hard disk drives
• List of IBM products

External links

• IBM Archive: Basic Storage Information
• IBM Archive: Collection of Disk Drive Articles
• Magnetic Disk Heritage Center
• A Quarter Century of Disk File Innovation, IBM Journal of Research and Development, 1981
• EE Times: The Eventful Evolution of Disk Drives
• IBM 1311 Disk Storage Drive Documentation
• IBM 2314 Direct Access Storage Manuals