A storage device (100, 100a-c), comprising: a non-volatile memory (120, 1220, 1230, 1240) comprising a plurality of non-volatile memory cells; a buffer memory (130, 1250) configured to temporarily store write data to be written to the non-volatile memory (120, 1220, 1230, 1240) or read data read from the non-volatile memory (120, 1220, 1230, 1240); and a controller (110, 110a-c, 116, 1210) configured to receive a sleep mode signal (S_SLP) from an external host (200, 1100), and calculate a data dump condition for writing the write data to the non-volatile memory (120, 1220, 1230, 1240), wherein, when the sleep mode signal (S_SLP) is received by the controller (110, 110a-c, 116, 1210), the controller (110, 110a-c, 116, 1210) is configured to block a first power supplied to the non-volatile memory (120, 1220, 1230, 1240) and set the buffer memory (130, 1250) to one of a first mode in which a second power is blocked from being supplied to the buffer memory (130, 1250) and a second mode in which the buffer memory (130, 1250) operates with low power based on the data dump condition, wherein the controller (110, 1 10a-c, 116, 1210) is configured to set the buffer memory (130, 1250) to the first mode when the data dump condition is satisfied based on at least one of a size of dump data and a writing condition of the non-volatile memory (120, 1220, 1230, 1240), and set the buffer memory (130, 1250) to the second mode when the data dump condition is not satisfied based on the at least one of the size of the dump data and the writing condition of the non-volatile memory (120, 1220, 1230, 1240), wherein the write data stored in the buffer memory (130, 1250) is written to the non-volatile memory (120, 1220, 1230, 1240) when the buffer memory (130, 1250) is set to the first mode. a non-volatile memory (120, 1220, 1230, 1240) comprising a plurality of non-volatile memory cells; a buffer memory (130, 1250) configured to temporarily store write data to be written to the non-volatile memory (120, 1220, 1230, 1240) or read data read from the non-volatile memory (120, 1220, 1230, 1240); and a controller (110, 110a-c, 116, 1210) configured to receive a sleep mode signal (S_SLP) from an external host (200, 1100), and calculate a data dump condition for writing the write data to the non-volatile memory (120, 1220, 1230, 1240), wherein, when the sleep mode signal (S_SLP) is received by the controller (110, 110a-c, 116, 1210), the controller (110, 110a-c, 116, 1210) is configured to block a first power supplied to the non-volatile memory (120, 1220, 1230, 1240) and set the buffer memory (130, 1250) to one of a first mode in which a second power is blocked from being supplied to the buffer memory (130, 1250) and a second mode in which the buffer memory (130, 1250) operates with low power based on the data dump condition, wherein the controller (110, 1 10a-c, 116, 1210) is configured to set the buffer memory (130, 1250) to the first mode when the data dump condition is satisfied based on at least one of a size of dump data and a writing condition of the non-volatile memory (120, 1220, 1230, 1240), and set the buffer memory (130, 1250) to the second mode when the data dump condition is not satisfied based on the at least one of the size of the dump data and the writing condition of the non-volatile memory (120, 1220, 1230, 1240), wherein the write data stored in the buffer memory (130, 1250) is written to the non-volatile memory (120, 1220, 1230, 1240) when the buffer memory (130, 1250) is set to the first mode.