Power conservation in data storage device by only starting the active state when the measured time indicates data is present on the interface

1. A storage device for storing data, comprising:

an interface controller connectable to a host via an interface, the interface controller having an active state capable of transmitting data to the host and an inactive state having a lower power consumption than the active state;

a medium for storing data;

a head for reading out data stored in the medium; and

a processor for executing a process comprising:

receiving a command for reading out data stored in the medium from the host,

determining timing when the data read out from the medium reaches the interface controller,

detecting native-command-queuing command data service,

determining whether to execute the data service during the preparation for reading the data from the medium,

performing the data service when an execution end time of the data service is earlier than the determined timing,

starting transition of the interface controller from the inactive state into the active state before the determined timing, and

changing the interface for the host into a power saving state when the native-command-queuing command data service is not executed and it is determined on the basis of the determined timing that a time for putting the interface into the power saving state is available, and restoring the interface to a data transferable state according to the determined timing when the interface is in a power saving state in which the data is not transferable.

2. A method for controlling a storage device for storing data, the storage device including an interface controller connectable to a host via an interface, the interface controller having an active state capable of transmitting data to the host and an inactive state having a lower power consumption than the active state, a medium for storing data, and a head for reading out data stored in the medium, the method comprising:

receiving a command for reading out data stored in the medium from the host;

determining timing when the data read out from the medium reaches the interface controller;

detecting native-command-queuing command data services;

determining whether to execute the data service during the preparation for reading the data from the medium;

performing the each data services when an execution end time of the data service is earlier than the determined timing;

starting transition of the interface controller from the inactive state into the active state before the determined timing; and

changing the interface for the host into a power saving state when the native-command-queuing command data service is not executed and it is determined on the basis of the determined timing that a time for putting the interface into the power saving state is available, and restoring the interface to a data transferable state according to the determined timing when the interface is in a power saving state in which the data is not transferable.