Abstract: Methods and apparatus for managing a cache which includes a number of dirty lines in which (a) the percentage of dirty lines in the cache is determined, (b) the cache is flushed if the determined percentage of dirty lines exceeds a predetermined threshold, (c) whether a state of a system is idle is determined based on at least two indicators including (i) CPU idle percentage, (ii) data bus busyness percentage, (iii) percentage of dirty lines, and (iv) I/Os per second, and (d) if the state of the system is determined to be idle, a line of the cache is flushed.

Abstract: A method and device for writing blocks from a client to a storage device. First and second caches are provided between the client and the storage device. An I/O management process accepts a write request from the client. If the write request is a write-back request, the I/O management process stores the blocks in the first cache, and transferring the blocks from the first cache to the second cache. If, on the other hand, the write request is not a write-back request, a write-through request is performed in which blocks are stored in the first cache, stored in the storage device, but not stored in the second cache. When the blocks are flushed from the first cache to store the blocks on the storage device, the dirty map of the cache header corresponding to the blocks is cleared from the second cache.