An operation method of a storage device configured to implement physical functions respectively corresponding to hosts includes receiving performance information from each of the host devices, setting a performance level of each of the physical functions to a first level, processing a command from a first host through a corresponding first physical function, changing a performance level of the first physical function to a second level based on the performance information and a performance serviced to the first host, and processing a second command from a second host through at least one second physical function corresponding to the second host prior to processing a subsequent first command from the first host, through the first physical function, based on a performance level of the at least one second physical function being the first level and the performance level of the first physical function being the second level.