| 摘要 |
Methods and associated apparatus for balancing the I/O request processing load within a plurality of controllers (102, 104) in a storage subsystem (100). The methods of the present invention are operable within interconnected controllers of a storage subsystem (100) to shift the processing of received I/O requests to less loaded controllers and to do so in a manner transparent to legacy attached host systems (122, 124). In a first embodiment of the present invention referred to as back-end load balancing, I/O requests are transferred from a first controller (102), to which the I/O request was directed by the attached host system (122, 124), to a second controller (104) for further processing. In this back-end load balancing embodiment, all write data associated with a write request as well as returned information including status or read data, is exchanged between the first (102) and second controllers (104) such that the first controller (102) performs all communication with the attached host system. In a second embodiment referred to as front-end load balancing, the first controller (102) receives an I/O request and transfers the request of a second controller (104). The second controller (104) then completes the I/O request including any requisite communication with the attached host system (222) to receive write data from the host system (222) or to return status or read data to the host system (222). The second controller (104) uses a false ID value, or otherwise substitutes itself for the first controller (102), in communicating with the attached host system (222) such that the attached host system (222) is fooled to believe that all communication is with first controller (102).
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