1. A computer-implemented method for accessing data stored in a distributed storage system, the method comprising: determining whether a copy of first data in a distributed storage system is stored in a distributed cache system, wherein data in the distributed cache system is stored in free storage space of the distributed storage system; accessing the copy of the first data from the distributed cache system, in response to determining that the copy of the first data is stored in a first data storage medium at a first computing system in a network; requesting a second computing system in the network to access the copy of the first data from the distributed cache system, in response to determining that the copy of the first data is stored in a second data storage medium at the second computing system; and accessing the first data from the distributed storage system, in response to determining that the copy of the first data is not stored in the distributed cache system, wherein the distributed cache system further comprises metadata providing a one-to-one mapping between the copy of the first data stored in the distributed cache system and the first data stored in the distributed storage system to enable the first data stored in the distributed storage system to be updated when the copy of the first data stored in the distributed cache system is updated.