According to one embodiment, a magnetic disk device configured to record data in a shingled-recording manner, wherein the device performs sequential write in a shingled-recording area on a magnetic disk such that data to be written in a write target track and data located in a one-forward track of the write target track are received on a volatile memory and then write with respect to the write target track is performed, and upon occurrence of an unexpected power cut, the device stores data unwritten in the shingled-recording area out of the data received on the volatile memory in a nonvolatile memory.

According to one embodiment, a magnetic disk device configured to record data in a shingled-recording manner, wherein the device performs sequential write in a shingled-recording area on a magnetic disk such that data to be written in a write target track and data located in a one-forward track of the write target track are received on a volatile memory and then write with respect to the write target track is performed, and upon occurrence of an unexpected power cut, the device stores data unwritten in the shingled-recording area out of the data received on the volatile memory in a nonvolatile memory.

According to one embodiment, a magnetic disk drive includes a flash memory adopting a Serial NAND that includes a plurality of Blocks. The magnetic disk drive determines one or more first Blocks to be used for write at backup, among the plurality of Blocks, based on a write time per the Block in the Serial NAND. The magnetic disk drive backs up data in a nonvolatile memory to the Serial NAND using a counter electromotive force of a spindle motor.

In a magnetic disk apparatus according to an embodiment, a power supply circuit generates second power from first power supplied by an external power supply, and generates third power when the first power is cut off. The third power is generated based on regenerative energy generated by stoppage of a motor. A controller writes data received from a host device to a magnetic disk via a cache area by the second power while the first power is supplied, and executes a backup process when the first power is cut off. The backup process is executed by disabling communication with the host device and saving content of the cache area to the first memory by the third power. A monitoring circuit keeps connection with the external power supply even when the first power is cut off. The controller enables communication with the host device when the first power is restored.