External storage control device and data transfer method between external storage control devices

摘要

In a data processing system in which main and sub disk storage devices 5, 10 are each under the control of individual disk control devices 3, 8, the write processing time is reduced by selectively sending data according to a command-chaining time between the main and sub disk control devices. A section 36 for judging cable length and function of the sub disk control device 8 estimates the command-chaining time between a pair of main and sub disk storage devices. A channel command analysing section 31 estimates the number of records to be transferred and the length of a record using a LOCATE RECORD command. The command judgement section 32 for the sub disk control device 8 optimises the command chain to be issued to the sub disk control device using the above-mentioned information. A command issuing section 35 then issues the optimised command chain to the sub disk control device 8. Thus, a shorter transmission time is realised by sending either individual records or an entire track of data. <IMAGE>