Method and device for file system

The invention relates to a method and a device for a file system. The file system comprises at least first logical storage area and second logical storage area, and the size of a logical block of the first logical storage area is different from that of a logical block of the second logical storage area. The method includes that in response to a file establishing request, a logical storage area for storing files is selected from the at least first logical storage area and second logical storage area, and the files are stored in the selected logical storage area. By means of the method and the device for the file system, variable length block size can be supported by direct and effective methods in the file system, and metadata and positioning expenses are not increased.