Destaging modified data blocks from cache memory

Details Destaging modified data blocks from cache memory Destaging modified data blocks from cache memory

1993-12-23

1996-07-30

Rudolph, Rebecca L.

395456, 395440, G06F 1200

Patent

active

055420664

ABSTRACT:
A controller for a disk array with parity and sparing includes a non-volatile cache memory and optimizes the destaging process for blocks from the cache memory to both maximize the cache hit ratio and minimize disk utilization. The invention provides a method for organizing the disk array into segments and dividing the cache memory into groups in order of least recently used memory locations and then determining metrics that permit the disk array controller to identify the cache memory locations having the most dirty blocks by segment and group and to identify the utilization rates of the disks. These characteristics are considered to determine when, what, and how to destage. For example, in terms of maximizing the cache hit ratio, when the percentage of dirty blocks in a particular group of the cache memory locations reaches a predetermined level, destaging is begun. The destaging operation continues until the percentage of dirty blocks decreases to a predetermined level. In terms of minimizing disk utilization, all of the dirty blocks in a segment having the most dirty blocks in a group are destaged.

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