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): m
Command action
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibilityflag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOSpartition table
p print the partition table
q quit without saving changes
s create a new empty Sundisklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (expertsonly)
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 4
First cylinder (1-2088, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G}(1-2088, default 2088):
Using default value 2088
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
说明：上面操作对sdb硬盘进行了分区操作，设为sdb4分区了（当然上面建立的主分区可以为1-4中的任意一个，我这里选择的4）。
第五步、对新建立的sdb4分区进行格式
[root@linuxidc ~]# mkfs.ext4 /dev/sdb4
mke2fs 1.41.12 (17-May-2010)
文件系统标签=
操作系统:Linux
块大小=4096 (log=2)
分块大小=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
1048576 inodes, 4192957 blocks
209647 blocks (5.00%) reserved for thesuper user
第一个数据块=0
Maximum filesystem blocks=4294967296
128 block groups
32768 blocks per group, 32768 fragments pergroup
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208,
4096000
正在写入inode表: 完成
Creating journal (32768 blocks): 完成
Writing superblocks and filesystemaccounting information: done完成
This filesystem will be automaticallychecked every 20 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
说明：将sdb4分区格式化为ext4格式，因为CentOS安装是系统的格式ext4，所以这里要注意一下。
第六步、格式后的sdb4分区添加为物理卷
[root@linuxidc ~]# pvcreate /dev/sdb4
Physical volume "/dev/sdb4" successfully created
相关阅读：
扩展Fedora 16虚拟机的根分区磁盘容量
Ubuntu Linux移动根分区