A data operating method, device, and system are provided. The method includes: receiving an operation instruction sent by a CPU; when the operation instruction is a read instruction, reading a first data block in the block device and returning to-be-read data in the first data block to the CPU; or when the operation instruction is a write instruction, writing, into a cache, to-be-written data indicated by the write instruction, and writing, into the block device, a second data block that includes the to-be-written data. The method is used to operate data in a block device.