linuxdebian挂载数据盘无报错，但查看时候显示64M

root@AY14042516351017741bZ:~# fdisk -S 56 /dev/xvdb

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
Partition 1 is already defined.  Delete it before re-adding it.

Command (m for help): wq
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
root@AY14042516351017741bZ:~# mkfs.ext3 /dev/xvdb1
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
19680 inodes, 78512 blocks
3925 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
10 block groups
8192 blocks per group, 8192 fragments per group
1968 inodes per group
Superblock backups stored on blocks:
        8193, 24577, 40961, 57345, 73729

Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 31 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
root@AY14042516351017741bZ:~# echo '/dev/xvdb1  /mnt ext3    defaults    0  0' >> /etc/fstab
root@AY14042516351017741bZ:~# cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
proc            /proc           proc    defaults        0       0
# / was on /dev/xvda1 during installation
UUID=34e4b8c4-016a-4003-8b4d-92aeb3cdc3c5 /               ext3    errors=remount-ro 0       1
/dev/scd0       /media/cdrom0   udf,iso9660 user,noauto     0       0
xenfs                   /proc/xen               xenfs   defaults        0 0
/dev/xvdb1  /mnt ext3    defaults    0  0
root@AY14042516351017741bZ:~# mount -a
root@AY14042516351017741bZ:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/xvda1             20G 1011M   19G   6% /
tmpfs                 248M     0  248M   0% /lib/init/rw
udev                  244M  116K  243M   1% /dev
tmpfs                 248M     0  248M   0% /dev/shm
/dev/xvdb1             75M  5.6M   65M   8% /mnt