1. A computer, comprising: a processor; a basic input/output system; and a main memory configured to load an instruction of the basic input/output system and an instruction of an operating system in the computer, wherein the processor, the basic input/output system and the main memory are coupled to each other, wherein the main memory comprises: one or more memory cards; and a memory controller, wherein a corresponding memory controller is configured for each memory card, wherein the processor is configured to: execute the instruction of the operating system; receive a first trigger instruction when executing the instruction of the operating system; execute a memory data migration instruction of the basic input/output system according to the first trigger instruction; and perform the following operations according to the memory data migration instruction of the basic input/output system to: determine a source memory card of to-be-migrated memory data; determine a backup memory card for the source memory card; and instruct a memory controller of the source memory card to migrate the memory data, wherein the memory controller of the source memory card is configured to: receive an instruction of the processor; and migrate the memory data of the source memory card to the backup memory card according to the instruction of the processor, wherein the processor is further configured to: set the source memory card and the backup memory card to a mirror mode; send a data read instruction to the memory controller of the source memory card, wherein the data read instruction is used to instruct the memory controller of the source memory card to read the memory data of the source memory card; and send a data write instruction to the memory controller of the source memory card, wherein the data write instruction is used to instruct the memory controller of the source memory card to write the read data back into the source memory card, wherein the memory controller of the source memory card is further configured to: read the memory data of the source memory card according to the data read instruction of the processor; receive the data write instruction sent by the processor; and send the read memory data of the source memory card to a memory controller of the backup memory card according to the mirror mode of the source memory card and the backup memory card, and wherein the memory controller of the backup memory card is configured to write the received memory data of the source memory card into the backup memory card.