Through use of the technologies of the present invention, one is able to store and to retrieve data efficiently. One may realize these efficiencies by coding the data and storing coded data that is of a smaller size than original data.

The present disclosure relates to data transmission methods, systems, and apparatuses. In one example method, a first device sends first information of a first data block to a second device. The second device searches, based on the first information, a first index for a second data block similar to the first data block, and sends second information of the second data block to the first device. The first device locally obtains, based on the second information, a reference block that is the same as the second data block, compresses a difference part of the first data block relative to the reference block to obtain first compressed information, and sends the first compressed information to the second device. The second device obtains the first data block based on the first compressed information and the second data block.