Method for copying data as well as method, device and system for reading data

The embodiment of the invention provides a method for copying data as well as a method, device and system for reading the data. The method for copying the data comprises the steps: confirming a data copying speed of copying data to a cache region according to the access frequency of the cache region, the load of a magnetic disc and the load of the cache region when the access frequency of the cache region is not more than a high frequency threshold value; and copying the data from the magnetic disc to the cache region according to the copying speed. The method for reading the data comprises the steps: judging whether read request access data are memorized in the cache region after receiving the read request which is used for accessing the magnetic disc; and confirming to read the read request access data from the cache region or the magnetic disc according to the load factor of the magnetic disc and the access balance rate of the cache region when the read request access data are memorized in the cache region. The embodiment of the invention is good for improving the overall performance of a memory system.