linux lvm 同一块硬盘多个逻辑卷

系统中有一个sda2是linux lvm格式的，对应了一个lvm的逻辑卷，怎么实现sda2对应二个或者多个逻辑卷呢，详细操作过程如下：

前面二篇文章，也是有关LVM的，每一步都说的很清楚，有兴趣的可以看一下

[root@localhost ~]# df -h    //缩小空间前
Filesystem                    Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root  356G   39G  299G  12% /
tmpfs                         3.9G   72K  3.9G   1% /dev/shm
/dev/sda1                     485M   40M  420M   9% /boot
/dev/mapper/VolGroup-lv_home   99G   23G   72G  22% /home 

[root@localhost ~]# umount /home/    //取消挂载

[root@localhost ~]# e2fsck -f /dev/mapper/VolGroup-lv_home      //磁盘检测
e2fsck 1.41.12 (17-May-2010)
第一步: 检查inode,块,和大小
第二步: 检查目录结构
第3步: 检查目录连接性
Pass 4: Checking reference counts
第5步: 检查簇概要信息
/dev/mapper/VolGroup-lv_home: 1580/5898240 files (4.4% non-contiguous), 6244001/23592960 blocks

[root@localhost ~]# resize2fs -p /dev/mapper/VolGroup-lv_home 85G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/mapper/VolGroup-lv_home to 22282240 (4k) blocks.
Begin pass 3 (max = 720)
正在扫描inode表          XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
The filesystem on /dev/mapper/VolGroup-lv_home is now 22282240 blocks long.

[root@localhost ~]# mount /home/  //在挂上去

[root@localhost ~]# df -h   //在看一下，分区情况
Filesystem                    Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root  356G   39G  299G  12% /
tmpfs                         3.9G   72K  3.9G   1% /dev/shm
/dev/sda1                     485M   40M  420M   9% /boot
/dev/mapper/VolGroup-lv_home   84G   23G   58G  29% /home    //变小了

[root@localhost ~]# lvreduce -L 85G /dev/mapper/VolGroup-lv_home     //减小home分区
  WARNING: Reducing active and open logical volume to 85.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv_home? [y/n]: y
  Reducing logical volume lv_home to 85.00 GiB
  Logical volume lv_home successfully resized

[root@localhost ~]# vgdisplay     //查看一下逻辑卷组的情况
  --- Volume group ---
  VG Name               VolGroup
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  7
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                3
  Open LV               3
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               465.27 GiB
  PE Size               4.00 MiB
  Total PE              119109
  Alloc PE / Size       115269 / 450.27 GiB
  Free  PE / Size       3840 / 15.00 GiB    //有可用空间3840个PE，15GB
  VG UUID               Vt2V4t-Byxs-tQqk-cY0h-IDE3-pabX-LUfkRS

//用VolGroup卷组中所有可用空间，创建逻辑卷tanktest卷，下午列举几个常用的
[root@localhost ~]# lvcreate --name tanktest -l 100%FREE VolGroup
  Logical volume "tanktest" created

//在VolGroup卷组中创建一个200M逻辑卷tanktest1
[root@localhost ~]# lvcreate -L 200 -n tanktest1 VolGroup   

//在VolGroup卷组中创建一个20G逻辑卷tanktest2
[root@localhost ~]# lvcreate -L 20G -n tanktest2 VolGroup   

//用VolGroup卷组中50%的可用空间,创建逻辑卷tanktest3
[root@localhost ~]# lvcreate -l 50%VG -n tanktest3 VolGroup   

[root@localhost ~]# mkdir /mnt/tanktest     //创建挂载目录

[root@localhost ~]# mkfs.ext4 /dev/VolGroup/tanktest     //格式化新建的逻辑卷tanktest
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=1 blocks, Stripe width=0 blocks
983040 inodes, 3932160 blocks
196608 blocks (5.00%) reserved for the super user
第一个数据块=0
Maximum filesystem blocks=4026531840
120 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
        32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208

正在写入inode表: 完成
Creating journal (32768 blocks): 完成
Writing superblocks and filesystem accounting information: 完成

This filesystem will be automatically checked every 27 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

[root@localhost ~]# echo '/dev/VolGroup/tanktest /mnt/tanktest    ext4    defaults        0 0' >> /etc/fstab  //自动挂载

[root@localhost ~]# reboot   //重启，检测一下是不是能自动挂载

[root@localhost ~]# df -h    //查看分区情况，新逻辑卷已正确挂载
Filesystem                    Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root  356G   40G  298G  12% /
tmpfs                         3.9G     0  3.9G   0% /dev/shm
/dev/sda1                     485M   40M  420M   9% /boot
/dev/mapper/VolGroup-lv_home   84G   23G   58G  29% /home
/dev/mapper/VolGroup-tanktest    15G  166M   14G   2% /mnt/tanktest