A cache storage method includes providing a storage cache cluster, comprising a plurality of cache storage elements, for caching I/O operations from a plurality of virtual machines associated with a corresponding plurality of virtual hard disks mapped to a logical storage area network volume or LUN. Responsive to a cache flush signal, flush write back operations are performed to flush modified cache blocks to achieve or preserve coherency. The flush write back operations may include accessing current time data indicative of a current time, determining a current time window in accordance with the current time, determining a duration of the current time window, and identifying a current cache storage element corresponding to the current time window. For a duration of the current time window, only those write back blocks stored in the current cache storage element are flushed. In addition, the applicable write back blocks are flushed in accordance with logical block address information associated with each write back block.
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