IBM 3380 direct access storage device

The IBM 3380 family of storage products meets the varied data storage requirements of today's large data processing systems. Advanced design and technology contribute to the excellent reliability. high performance and impressive environmental characteristics of the IBM 3380. It requires less electrical power, generates less heat, requires less floor space, and is priced less per megabyte when compared on an equal capacity basis with previous products.

Standard and Extended Capability models

IBM 3380s are identified as Standard or Extended Capability models. Extended Capability models have all the features of the Standard models and have Device Level Selection, a function designed to further improve availability and performance. Extended Capability models also can store or be upgraded to store 5.04 billion bytes (or gigabytes) in a single unit. Each IBM 3380 has four functionally independent actuators which access data stored on the two head and disk assemblies (HDAs) within each unit.

There are seven models of the IBM 3380 family: four 'A' models and three 'B' models. 'A' models (heads of string) contain additional logic to perform string controller functions. All models store data in count-key-data format with capacities of either 2.52 or 5.04 gigabytes of data, depending on the model.

IBM 3380 models available are:

Purchased Models AD4 and BD4 can be field-upgraded to the double-capacity AE4 and BE4 models, respectively. The A04 can be field-upgraded to an AA4. All models are attached to processor channels through storage directors on the IBM 3880 Storage Control. The 'A' models with two string controllers (the Dynamic Path Selection function) support connection to two separate storage directors, providing improved availability and performance. These models provide two paths for data flow between the IBM 3880 Storage Control and the individual actuators in the string. The internal paths for the Extended Capability models have been enhanced to allow simultaneous data transfer from any two actuators within the string, even within the same HDA. This function, Device Level Selection combined with Dynamic Path Selection, provides improved data availability and performance. In the MVS environment, the Dynamic Path Reconnect capability of the System/370 Extended Architecture operating system exploits these hardware functions to provide increased performance.

A string of Standard model 3380s can consist of a single 3380 Model A04 or AA4 and up to three 3380 Model B04 units. A string of Extended Capability 3380s can consist of one 3380 Model AD4 or AE4 and up to three 3380 Model BD4 and BE4 units, in any combination. Two strings of 3380s can be attached to each storage director of a 3880 Model 3 or cache storage control Model 23. An A04 string is not supported by the Model 23. Strings headed by an AA4, AD4 or AE4 must attach to two storage directors (usually on two separate 3880 Storage Controls). An AA4 string and an Extended Capability string can be attached to the same storage directors.

• A string of IBM 3380s with 16 actuators can provide from 10.08 gigabytes to 20.16 gigabytes, depending on model configuration.
  
  
• Models AA4, AD4 and AE4 provide Dynamic Path Selection which make two string controllers available with independent paths for simultaneous command and data transfers to and from actuators, These models provide improved data availability and subsystem performance.
  
  
• In all models, actuators can operate independently. A maximum of two actuators in a string can transfer data simultaneously. Extended Capability models have Device Level Selection, allowing data transfer from any two actuators.
  
  
• Models AD4 and AE4 have an operator interface panel with lights that indicate path and actuator status for all actuators on the string. The panel also has operator switches to assist with problem determination, system recovery and backup procedures.
  
  
• Standard models of the 3380 can be used with the Speed Matching Buffer feature on the 3880 Storage Control Model 3 to attach to block multiplexer channels with data rates of less than three megabytes per second. Data transfers at 1.5 megabytes per second in this Speed Matching Buffer configuration.
  
  
• The 3880 Storage Control can attach to IBM 303X, 308X, and 43XX processors having three megabyte-per-second channels.
  
  
• For high-performance applications, IBM 3380 performance can be improved by attachment to the 3880 Storage Control Model 23. The IBM 3380 Model A04, however, is not attachable to a 3880 Storage Control Model 23.
  
  
• Two strings of IBM 3380s can be attached to each storage director on the IBM 3880 Storage Control.
  
  
• Command retry enables the IBM 3380 to recover from some errors without having to utilize processor error recovery programs.
  
  
• The Maintenance Device, containing a microprocessor, is used by IBM Customer Engineers to help minimize the time needed to diagnose and repair problems. Guided maintenance planning is also part of the complete maintenance approach IBM utilizes in the servicing of IBM 3380 storage products. The IBM 3380's engineering design includes field-replaceable units. This can help the IBM Customer Engineer replace parts to correct failures more quickly.
  
  Maintenance of a single actuator in any model, or a controller in a Dynamic Path Selection model, can generally be performed without interruption to the operation of the remainder of the string.