The Type DSS270 Disk Storage Subsystem is available for use in Series 6000 and 600 systems. The large capacity Type DSS270 provides very fast access to over 15 million data characters per storage unit through a service-proven fixed head-per-track design. The subsystem can control 20 storage units to provide over 307 million characters of direct-access storage. A Dual-Channel option permits simultaneous access to the subsystem by two processors or simultaneous dual-channel access by a single processor.
The storage capacity of the Type DSU270 Disk Pack Drive is 15.3 million 6-bit characters. Up to 20 drives can be connected to one controller to provide over 307 million characters of storage.
Maximum transfer rate is 333,000 6-bit characters per second. This rate may be doubled through dual-channel simultaneity.
Since the read/write mechanism on the DSU270 is of the fixed head-per-track design, access time to all disk locations is relatively constant and very fast. Average record access time is 26 milliseconds. Maximum is 50.3 milliseconds.
Data is grouped in a total of 40,000 continuously addressable sectors of 384 characters each per disk pack drive. A maximum subsystem thus can address up to 800,000 data sectors.
The Disk Storage Controller (DSC270) handles up to four file electronics units. Each file electronics unit (DFE270) controls up to five disk pack drives, providing a total subsystem capacity of 20 DSU270s. The controller communicates with the processor via one high-speed channel, or two channels when the Dual-Channel option is installed.
An option is provided in the controller for an additional data channel. With this option, independent and simultaneous data transfer and command communication is allowed between the controller and one or two processors, with the restriction that data transfer simultaneity cannot occur within the same file electronics unit. The option can be used with one processor to increase the effective data transfer rate or used to allow two separate processors to access the same data base.
DUAL-CHANNEL INTERFERENCE PROTECTIONTo prevent access interference in dual-channel configurations, a file electronics device is automatically reserved for a particular channel after that channel has established communication with a successful select command.
A hardware sector count feature provides file protection by allowing the software to limit the number of continuous data sectors that can be read or written with a single data transfer command. The sector count limit can vary from 1 to 4,096.
Nine checks are performed on control information and data in the subsystem. These checks consist of data parity and timing, and control information parity and validity. Additionally, nine hardware conditions are continually monitored.
Incorporated in the hardware is an error detection feature that enables the subsystem to identify an error condition on reading a record. Determination of correctability and correction itself may be performed under software control.
A minimum subsystem configuration is one DSC270 Controller, one DFE270 File Electronics Unit and one DSU270 Disk Pack Drive. The illustration below represents a maximum configuration, with over 307 million characters of data being shared by two separate data processing systems via the controller’s Dual-Channel Option.
Specifications remain subject to change in order to allow the introduction of design
improvements.
© 1971, Honeywell Information Systems Inc.
11 1.0021.1300.O-G72
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