Write cache destaging

摘要

Disclosed is a system for controlling write actions to a plurality of data storage devices, the system comprising a plurality of write caches, wherein each cache is associated with a set of said data storage devices; and a controller adapted to issue write permissions to said data storage devices, said write permissions including a permission to perform a data destage operation from a cache to a data storage device; wherein each cache has a first performance score expressed as the difference between the number of data destage operations said cache has in flight and the maximum number of data destage actions said cache is permitted to issue in parallel; and wherein the controller is adapted to offer a data destage operation permission to the cache in said plurality of caches associated with the highest first performance score.

主权项

1. A system for controlling write actions to a plurality of data storage devices, the system comprising:
a plurality of write caches, wherein each cache is associated with a set of said data storage devices; and a controller adapted to issue write permissions to said data storage devices, said write permissions including a permission to perform a data destage operation from a cache to a data storage device, wherein each cache has a first performance score expressed as the difference between the number of data destage operations said cache has in flight and the maximum number of data destage actions said cache is permitted to issue in parallel, wherein the controller is adapted to offer a data destage operation permission to the cache in said plurality of caches associated with the highest first performance score, each data storage device has a second performance score expressed as the difference between the number of data destage operations said device has in flight and the maximum number of data destage operations said device is permitted to handle in parallel, each cache is adapted to pass an offered data destage operation permission onto the data storage device in its set having the highest second performance score, each data storage device is adapted to refuse the offered data destage operation permission in case the number of data destage operations said device has in flight equals the maximum number of data destage operations said device is permitted to handle in parallel, and each cache is adapted to respond to such a refusal by passing the offered data destage operation permission onto the data storage device in its set having the next largest difference between the number of data destage operations said device has in flight and the maximum number of data destage operations said device is permitted to handle in parallel until one of said data storage devices accepts the offer or until all data storage devices have rejected the offer.