| 摘要 |
Disclosed are a method and apparatus, in a data storage environment with multiple devices sharing data, for writing data to one such device in a manner that indicates that the data need not be destaged to a lower tier of the storage hierarchy. As a specific example, a host computer system may issue a write command to a controller that signals the controller that it is not necessary to destage the data from the controller cache because the data has not been modified by the host. In a preferred embodiment, the controller's cache is an extension of the host's cache, rather than a duplication. To achieve this, the controller needs to know: 1) what data, being requested by the host, is being cached by the host, and should not be cached by the controller, and 2) what data has been cast out of the host's cache, and should now be cached by the controller.
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