Host Driver Command to Transport Mode Conversion
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Solution Overview
Problem
Existing systems lack a mechanism to convert command mode I/O operations to transport mode I/O operations without modifying applications, especially when the original source code is not available or it is economically unfeasible to rewrite the application.
Innovation Solution
A system that intercepts and converts command mode control words into transport mode control words using an SSCH layer or channel subsystem layer, determining if the storage device accepts transport mode control words by checking a flag, allowing communication between host and storage devices using FICON connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If applications directly call low level routines to transmit command mode data, then the applications can communicate with storage devices using existing command mode interfaces, but the communication efficiency is reduced due to multiple back and forth exchanges between host and storage device
Solution Approach 1:
The patent introduces a driver layer as an intermediary between the application and the storage device. This driver intercepts command mode control words from the application and converts them into transport mode control words, enabling efficient transport mode communication without requiring application modification. The driver acts as a mediator that translates between the two protocols, resolving the contradiction between maintaining application simplicity and achieving communication efficiency.
2Productivity
If the application is rewritten to use transport mode instead of command mode, then the data transfer efficiency is improved by reducing back and forth communication, but the development cost and complexity increase due to source code modification requirements
Solution Approach 1:
The driver serves as an intermediary that sits between the unmodified application and the storage device. It automatically performs the conversion from command mode control words to transport mode control words, allowing the application to continue using familiar command mode interfaces while actually communicating using efficient transport mode. This eliminates the need for expensive application rewriting while still achieving the performance benefits of transport mode.
Solution Approach 2:
The patent creates a virtual copy of the command mode interface at the driver level. The driver intercepts and processes command mode control words, then translates them into transport mode control words for actual communication. This copying approach allows the application to work with familiar command mode syntax while the underlying communication uses efficient transport mode, avoiding the need to modify or recreate the application.
3Productivity
If a conversion mechanism is introduced to transform command mode control words to transport mode control words, then the data transfer efficiency is improved, but the system complexity increases due to the additional conversion layer
Solution Approach 1:
The driver acts as an intermediary layer in the existing I/O architecture, positioned between the application and the channel subsystem. It intercepts control words at a natural breakpoint in the data flow and performs conversion without requiring changes to the overall system architecture. This approach adds minimal complexity by leveraging the existing driver model rather than introducing a completely new conversion mechanism.
Solution Approach 2:
The conversion from command mode control words to transport mode control words is performed in advance, before the actual I/O operation is executed. The driver prepares the transport mode control words by intercepting and transforming the command mode control words early in the processing chain, so that the subsequent communication with the storage device can proceed efficiently without requiring real-time conversion during data transfer.
Data Source
AI summary
Communicating between a first device and a second device includes the first device generating command mode control words for communication with the second device, the first device converting the command mode control words into transport mode control words prior to transmitting the control words to the second device, the first device receiving transport mode control words from the second device, and the first device converting the transport mode control words received from the second device into received command mode control words. An application running on the first device may generate command mode control words for communication with the second device. The application may directly provide command mode control words to an ssch or channel subsystem layer. The first device may convert the command mode control words into transport mode control words using an ssch or channel subsystem layer. The first device may be a host computing system.