I tried to view the superblock by command "dd" in ext3 file system.
dd if=/dev/sda3 bs=4096 skip=1 count=1 of=superblock
But the result in superblock file is not correct(I compare the value of Inodes count I got from dumpe2fs). The device file /dev/sda3 is started at the boot block and then the superblock of the group0? And another question is the boot block and superblock's size are both BLOCKSIZE(here is 4096)? The disk format of ext2/ext3(I think they are the same) are shown below: