A primary node-standby node data transmission method includes an indication that a control node obtains an operation log generated by a primary node, where the operation log includes at least one operation record, and each operation record indicates a record of performing, by the primary node, a write operation on a local cache or a storage unit in a storage device. The method further includes the control node determining a first storage unit set that corresponds to a first standby node, the control node determining a second storage unit set that corresponds to the at least one operation record, the control node obtaining an operation record from the operation log, and the control node sending the corresponding operation record to the first standby node, where the storage unit intersection set is an intersection set of storage units in the first storage unit set and the second storage unit set.