The present invention relates to a technique for controlling a disk device that performs writing/reading with respect to a storage medium such as a HDD (Hard Disk Drive), a DVD (Digital Versatile Disk), or the like and a memory medium such as an FD (Floating Disk) or the like. One of the background arts relating to the technique for controlling the disk device is disclosed in Japanese Patent Laid-open No. 2005-141863. In the disk device, there is a problem that an I/O (Input/Output) performance varies according to an elapsed time of a disk device. Accordingly, an operator generally decides a threshold value of the I/O performance after the user of the disk device is experienced. This threshold value becomes an evaluation criterion for judging whether or not the user of the disk device needs an initial performance test by a service man when the user of the disk device requests a performance test (when initial performance test is requested). However, if the threshold value is set to a constant value or is set to a value according to an average or a standard deviation obtained by analyzing a historical data in many cases, it is difficult to reflect all the case (circumstance) of the I/O performance of the disk device and may make the judgment of whether or not the I/O performance of the disk device is good or bad in view of the user's desire. For example, if the I/O performance is remarkably improved from the threshold value set, the user thinks that the I/O performance is good, whereas if the I/O performance is deteriorated, the user thinks that the I/O performance is bad. In particular, in the system that the performance is improved by using the firmware and the firmware is updated in the ordinary case in order to cope with various requests, the threshold value may be adjusted after updating of the firmware. At that time, the threshold value may be deviated from the user's desired value. Further, as a result of analysis of user's desire, since the request about a performance test and a request for the firmware update are completely different things, it is difficult to adjust the threshold value after the firmware update is performed. Therefore, there is a problem that if the threshold value is set to the value that does not reflect the user's desire, the I/O performance may be evaluated as a wrong result when the performance test is performed with respect to the disk device by the service man, or that the quality of firmware cannot be verified by the user. An object of the present invention is to provide a technique of performing the initial performance test (initial I/O performance test) with respect to a disk device without using the service man by a user who performs the performance test using an arbitrary method. Another object of the present invention is to provide a technique of accurately performing the initial performance test with respect to a disk device without giving a feeling of difficulty to the user who performs the performance test using an arbitrary method and is new to the I/O performance test. The present invention has been thought of in view of the foregoing points, and for the object, in accordance with the present invention, there is provided a disk device including: a performance test function for performing a performance test with respect to a storage medium in the disk device, wherein a performance test method of the performance test includes a firmware update step of updating a firmware with respect to the disk device, and the performance test method does not include the firmware update step. Further, in accordance with the present invention, there is provided a disk device including: a performance test function for performing a performance test with respect to a storage medium in the disk device; and a performance test method selection function for selecting a predetermined performance test method for performing the performance test with respect to the storage medium in the disk device. Further, in accordance with the present invention, there is provided a disk device including: a performance test function for performing a performance test with respect to a storage medium in the disk device; and a performance test method selection function for selecting a performance test method including a firmware update step in order to perform the performance test with respect to the storage medium in the disk device. Further, in accordance with the present invention, there is provided a disk device including: a performance test function for performing a performance test with respect to a storage medium in the disk device; and a performance test method selection function for selecting a performance test method for performing the performance test with respect to the storage medium in the disk device. Further, in accordance with the present invention, there is provided a disk device including: a performance test function for performing a performance test with respect to a storage medium in the disk device; and a performance test method selection function for selecting one from among a plurality of performance test methods for performing the performance test with respect to the storage medium in the disk device, wherein the plurality of performance test methods includes a first performance test method for not including a