IBM 3370 Direct Access Storage Device
- Models A1, B1, A11, and B11 announced January 30, 1979 and withdrawn August 5, 1986
- Models A2, B2, A12 and B12 announced September 15, 1983
The 3370 direct access storage device (DASD) was an advanced fixed-media disk unit that initially provided 571.3 megabytes of auxiliary storage for IBM's 4331 and 4341 processors and the IBM System/38 midrange computer. Up to four 3370 devices could be attached to any System/38 Model 5 for an additional 2,285.5 megabytes of auxiliary storage.
Average seek time was 20 milliseconds and the nominal data rate was 1.859 megabytes per second.
Two 3370s were available in February 1980 for attachment to System/38: Model A11 attached to the IBM 5381 System Unit Model 5, and up to three Model B11s could be connected through an A11 unit.
At announcement, a Model A11 could be leased for $900 a month, rented for $1,058 a month or purchased for $35,100. Corresponding charges for each B11 unit were $600, $705 and $23,400.
Models A2, B2, A12 and B12
The IBM 3370 Direct Access Storage model series 2, which includes Models A2, B2, A12 and B12, adds new capacity, price/performance and configuration flexibility in fixed block DASD architecture for the 4341, 4361, 4381 systems and System/38. The IBM 3370 model series 2 offers 729.8MB per drive which represents a 27 percent increase over the model series 1, which included Models Al, B1, All and B11. Being identical in track layout and block size, the model series 2 can be added to existing applications on supported systems. The performance improvement is achieved by reducing the average seek time 5 percent, from 20 ms to 19 ms. This new model series gives additional flexibility by allowing the intermixing of model series 1 and model series 2 drives on the same string on supported systems. This makes possible new configurations and adds improved cost-effective capacity to existing configurations as they grow.
The new Models A2 and A12 contain both a controller and disk drive. The new Models B2 and B12 contain just the disk drive. Each disk drive has two actuators which provide independent access to half of the storage
Highlights
Model A2 is a single-drive disk storage unit with two actuators and associated control for attachment to 4341, 4361 and 4381 processors. This model provides logic for attachment of up to three 3370 Model B1 or B2 units intermixed in any combination.
Model B2 is a single-drive disk storage unit with two actuators. Up to three 3370 Model B2 units may be attached to a 3370 Model Al or A2 when attached to a 4341, 4361 or 4381.
Model A12 is a single-drive disk storage unit with two actuators and associated control for attachment to System/38 Models 4, 5, 7 and 8 with a 3370 attachment adapter. The Model A12 provides logic and power for attachment of up to three 3370 Model B11 or B12 units intermixed in any combination.
Model B12 is a single-drive disk storage unit with two actuators. Up to three 3370 Model B12 units may be attached to a 3370 Model All or A12.
The model series 2 contains two actuators in each unit, providing independent access to half of the storage. Each unit of the model series 2 contains two logical direct access storage volumes, each with its own address.
The model series 2 attaches by means of the IBM 3880 Storage Control Models 1, 2 or 4 to the 4341, 4361 and 4381. On the 4361, attachment may also be accomplished via the DASD/8809 adapter. For the System/38, attachment is made through the disk storage attachment feature.
Fixed block architecture is incorporated in the 3370 model series 2 and model series 1. It provides for recording data in permanent preformatted 512-byte blocks. It also provides more efficient utilization of the disk surface for data and simpler, more flexible system attachment. In addition, the fixed block concept frees the user from concerns with the physical geometry of the disk drive.
The 3370 model series 2 contains the same film head technology and circuit design as the model series 1. These factors contribute to high performance and dependability.
The capacity of the 3370 model series 2 is 729.8MB per drive, compared with 571.2MB for the model series 1. This increase is achieved by adding 208 storage cylinders per actuator of identical organization and capacity to those of the model series 1. Identical in track layout and block size, the model series 2 can be added to existing applications on systems supporting model series 1.
Performance improvement results from a reduction in average seek time from 20 ms on the model series 1 to 19 ms on the model series 2. It is accomplished through an improved servo design to control actuator positioning.
The optional string switch feature allows attachment of the 3370 Models Al and A2 to a second storage director or DASD adapter. The two storage directors may be on the same processor or different processors. Switching between the two storage directors or DASD adapter is under program control.
Hardware support
The 3370 models can be attached only to specific 4300 series processors and the System/38. The 3370 Models A2 and 82 can be attached to 4300 processors; 3370 Models A12 and B12 are designed for attachment to System/38 Models 4, 5, 7 and 8. Models of the 3370 should be attached only to the systems for which they are designated.
The 3370 Models A2 and A12 require the following systems attachments:
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- DOS/VSE Advanced Functions
- VSE/System Product
- VSE/SIPO/E
- VM/System Product
The model series 2, like the model series 1, requires no preventive maintenance because of the following reliability, availability and serviceability characteristics:
- Sealed head and disk assembly
- Fixed media design
- Advanced logic technology with low failure rate
- Advancements in fault detection, isolation and identification
- Error correction code circuitry
- Improved error logging and symptom definition
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200-415V* 3-phase, 60Hz 4-wire or 50Hz 5-wire.
* System/38 IBM 5381 System Unit with 235V or 408V requires 415V.
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