1. A system for storing data of files comprising: a first storage system which includes a plurality of first type magnetic disk devices, each of which has a first type interface, and a disk array control processor configured to configure a first type logical unit classified into a first storage class by using the plurality of first type magnetic disk devices; a second storage system, which includes a plurality of second type magnetic disk devices, each of which has a second type interface which is different from the first type interface, and a disk array control processor configured to configure a second type logical unit classified into a second storage class by using the plurality of second type magnetic disk devices; and a file access control processor, coupled to the first storage system and the second storage system, which is configured to manage files stored in the first type logical unit classified into the first storage class and the second type logical unit classified into the second storage class, wherein the file access control processor is configured to migrate a file between the first type logical unit classified into the first storage class and the second type logical unit classified into the second storage class.