Patent ID: 6321298
Filing Date: 2001-11-20
Classification: G06F

Abstract:
A synchronization method for use in a storage system having multiple active controllers each processing I/O requests and a set of storage devices, the controllers each having an associated mirror cache, an associated read cache, and an associated write cache different from said mirror cache, the method including:in response to a write command to write first data to the storage devices, a first one of the active controllers writes the first data to the storage devices and to its own associated write cache and copies the first data to mirror caches associated with one or more other controllers that did not perform the write command; andin response to a read command to read second data from the storage devices, a second active controller checks for the data in its own associated mirror cache and, (i) if the second data is in its own associated mirror cache, returns the second data to a host computer that issued the read command; and, (ii) if the second data is found by the second active controller check not to be in its associated mirror cache, the second controller checks for and returns the second data to the host according to the following priority: first, from its own associated write cache; second, from its own associated read cache; and third from the storage devices.