An electronic storage device includes a first memory segment having at least one source block to store information, a second memory segment having at least one backup block corresponding to the source block to make a backup of the information in a LSB memory page of the source block and a control unit connecting with said first memory segment and second memory segment. The control unit reads/writes the first memory segment and second memory segment through two different signal channels respectively. The information can be simultaneously written into the first and second memory segment to get a backup of the information so that the information can be stored safely. The control unit recycles the backup block of the second memory segment not only after the source block of the first memory segment entirely finishes writing the information but also after the source block is erased up in order to release the storage space of the backup block.