Patent ID: 7571293
Filing Date: 2009-08-04
Classification: G06F

Abstract:
1. A method of processing input/output (I/O) commands of a first type of point-in-time (PIT) copy operation in a data processing system, the data processing system including a host computer system having an application operative to generate the I/O commands for the first type of PIT copy operation, the first type of PIT copy operation being directed to respective storage volumes of a data storage system that is capable of performing a second type of PIT copy operation, the method being performed as part of an emulation of the first type of PIT copy operation, comprising: translating selected ones of the I/O commands of the first type of PIT copy operation to corresponding I/O commands of the second type of PIT copy operation; carrying out the I/O commands of the second type of PIT copy operation resulting from the translation; returning results to the application according to the first type of PIT copy operation such that the application is unaware of the use of the second type of PIT copy operation; determining whether the I/O commands of the first type of PIT copy operation require modification for purposes of the emulation, and if so whether they are of a back-end type or an out-of-band type, the back-end I/O commands requiring modification of results reported to the application upon completion and the out-of-band I/O commands requiring substitution by corresponding I/O commands of the second type of PIT copy operation for purposes of the emulation; for those of the I/O commands not requiring modification for purposes of the emulation, processing such I/O commands without modification via an I/O subsystem of the host computer; for the back-end I/O commands, (i) setting an intercept condition, (ii) processing the back-end I/O commands via the I/O subsystem, and (iii) upon completion of the back-end I/O commands with the intercept condition set, modifying results of the back-end I/O commands so as to indicate to the application that the first type of PIT copy operation can be performed on the storage volumes to which the first type of PIT copy operation is directed; and for the out-of-band I/O commands, (i) processing corresponding I/O commands of the second type of PIT copy operation in lieu of the out-of-band I/O commands, and (ii) upon completion of the processed I/O commands, returning corresponding results to the application as though the out-of-band I/O commands had been processed by the I/O subsystem.