The CACHE Design In Network Storage Array

With the development of computer and network technology, storage technology has developed to network storage from local storage.Disk storage array(storage array for short)is one of the main network storage equipments,its access speed has become the bottleneck in the storage system.There is temporal and spatial locality when the user host access the data on the disk,so if there is a data buffer between the user host and the disk, which resembles high speed buffer CACHE between CPU and main memory in the computer system, the storage array can access the disk with a lower frequency and a better performance.The main points of this thresis are design and implement of the CACHE module:1. The memory management of CACHE module.The memory is managed by CACHE module is a fraction of the main memory in the storage array controller, it devides this fraction of main memory into four pieces, and each piece is managed by a submodule of CACHE that is devided according to the function.2. The access manner on CACHE and the data replacement strategy. We adopt writeback way(when CACHE received the data that user host is ready to write into disk it replys success to the user host and then the CACHE write the data into the disk insteadly) to improve the access performance of storage array and the hit ratio when reading data from CACHE.In order to improve the reading performance we designed intelligent prefetch algorithm which also can improve the hit ratio.At the same time it adopts multithread the asychronous way that can decrease the waiting time of host.3. Data security.CACHE module backups all the data in the other controller's cache to guarantee the safty and coherence of data in CACHE, it also gives details of safely access data technology when the storage array suffers accidents such as power off.