Method for a source storage device sending data to a backup storage device for storage, and storage device

A method for a source storage device to send data to a backup storage device over multiple backup time periods, wherein each backup time period is assigned a period ID, wherein the source storage device includes a processor and a cache;

• the method being performed by the processor and comprising:
• receiving multiple write data requests in a current backup time period, wherein each write data request includes data;
• reading a first period ID recorded in a period ID table, wherein the first period ID corresponds to the current backup time period;
• modifying each of the write data requests received in the current backup time period by attaching the first period ID to the data of said each write data request;
• writing each of the modified write data requests into the cache, wherein the cache storing write data requests each having an attached period ID corresponding to a backup time period in which said each write data request stored in the cache is received by the source storage device;
• determining that a backup task corresponding to the current backup time period is triggered, wherein the triggering of the backup task moves the source device into a next backup time period;
• identifying a second period ID, wherein the second period ID corresponds to a previous backup time period up to which data of write data requests received by the source storage device have been duplicated to the backup storage device;
• obtaining from the cache data of write data requests stored in the cache that are received after the backup time period corresponding to the second period ID and up to the current backup time period;
• and
• sending the obtained data to the backup storage device.