使用Linux的LVM在不丢失数据的情况下删除正在使用的硬盘或分区

作者：iceblood(刘宏光)

      大多数文章介绍的都仅仅是添加硬盘以及调整分区大小，但很少有安全的彻底卸掉其中一个分区或硬盘的，这里重点介绍一下这个。

    情况介绍：

一、由于硬盘或者分区的操作方式其实都一样，所以我这里就以分区为例。

二、/home分区2.6G，由如下pv组成：

/dev/sda5  100M

/dev/sda6   200M

/dev/sda7   300M

/dev/sda8   400M

/dev/sda9    500M

/dev/sda10  600M

/dev/sda11  500M

很碎对吧？^_^因为测试。

三、随机写了一堆文件进去，用量达到了2G，空闲500M

四、准备将sda6这个200M的PV卸掉（卸掉的容量必须小于空闲容量）

好了开始具体操作了。

卸载分区（缩小操作必须卸载才能进行）：

umount /home

缩小分区：

e2fsck -f /dev/liuhg_disk/home

resize2fs /dev/liuhg_disk/home 2200M

 首先将分区缩小到2200M这是为了给sda6腾出空间，sda6为200M，而我腾出了400M，因此应该是足够的。

缩小逻辑卷：

lvreduce -L 2200M /dev/liuhg_disk/home

分区缩小了用到的逻辑卷也要随着缩小，并查看PV使用的状态：

pvdisplay -m

显示如下：

    --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               liuhg_disk
  PV Size               103.26 MiB / not usable 3.26 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              25
  Free PE               0
  Allocated PE          25
  PV UUID               5lnx52-b4jc-OOfZ-f2QA-ttdQ-DZeD-Ce3rb3
  
  --- Physical Segments ---
  Physical extent 0 to 24:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     0 to 24
  
  --- Physical volume ---
  PV Name               /dev/sda6
  VG Name               liuhg_disk
  PV Size               203.92 MiB / not usable 3.92 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              50
  Free PE               0        <-----太悲剧了，sda6里写满了数据一点不剩
  Allocated PE          50    <-----这50PE的数据要挪走才行，否则数据就丢了，并且存放的地方也必须是连续的至少50PE
  PV UUID               S2ane6-nlFG-uSNR-35NP-Yxa6-cXRb-r8E8mK
  
  --- Physical Segments ---
  Physical extent 0 to 49:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     25 to 74
  
  --- Physical volume ---
  PV Name               /dev/sda7
  VG Name               liuhg_disk
  PV Size               305.89 MiB / not usable 1.89 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              76
  Free PE               76  <---这个分区有76个空余，因此预计装那50个是不会有问题的
  Allocated PE          0
  PV UUID               9CFnlx-CAEw-CSul-Rig9-FiCN-zK0a-oGmTEP
  
  --- Physical Segments ---
  Physical extent 0 to 75:
    FREE
  
  --- Physical volume ---
  PV Name               /dev/sda8
  VG Name               liuhg_disk
  PV Size               407.87 MiB / not usable 3.87 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              101
  Free PE               60
  Allocated PE          41
  PV UUID               X0I8p0-x2xr-2xLG-QQD4-jbtS-3C4i-xPn4Bl
  
  --- Physical Segments ---
  Physical extent 0 to 40:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     471 to 511
  Physical extent 41 to 100:
    FREE
  
  --- Physical volume ---
  PV Name               /dev/sda9
  VG Name               liuhg_disk
  PV Size               509.84 MiB / not usable 1.84 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              127
  Free PE               0
  Allocated PE          127
  PV UUID               avJQaA-oMKt-NEoJ-ojBK-2Csc-1dca-1mh6Ue
  
  --- Physical Segments ---
  Physical extent 0 to 126:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     225 to 351
  
  --- Physical volume ---
  PV Name               /dev/sda10
  VG Name               liuhg_disk
  PV Size               603.98 MiB / not usable 3.98 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              150
  Free PE               0
  Allocated PE          150
  PV UUID               JlMIAF-A49n-M6HA-ZLXf-d8nS-pfZr-YeQsKT
  
  --- Physical Segments ---
  Physical extent 0 to 149:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     75 to 224
  
  --- Physical volume ---
  PV Name               /dev/sda11
  VG Name               liuhg_disk
  PV Size               478.47 MiB / not usable 2.47 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              119
  Free PE               0
  Allocated PE          119
  PV UUID               xnHJNA-tDVx-dryX-KM1x-g96Y-sptI-9iUOcU
  
  --- Physical Segments ---
  Physical extent 0 to 118:
    Logical volume      /dev/liuhg_disk/home
    Logical extents     352 to 470

将sda6设置为离线状态：

pvchange -xn /dev/sda6

使用pvdisplay -m

显示如下：

……

  --- Physical volume ---
  PV Name               /dev/sda6
  VG Name               liuhg_disk
  PV Size               203.92 MiB / not usable 3.92 MiB
  Allocatable           NO      <-----表示已经关闭了该PV
  PE Size               4.00 MiB
  Total PE              50
  Free PE               0
  Allocated PE          50
  PV UUID               S2ane6-nlFG-uSNR-35NP-Yxa6-cXRb-r8E8mK

……
   将sda6的数据移走：

pvmove -i 1 /dev/sda6

-i 1是每1秒钟报告一次数据迁移的进度。

[root@liuhg /]# pvmove -i 1 /dev/sda6
  /dev/sda6: Moved: 38.0%
  /dev/sda6: Moved: 84.0%
  /dev/sda6: Moved: 100.0%

重新用pvdisplay -m

显示如下：

……

  --- Physical volume ---
  PV Name               /dev/sda6
  VG Name               liuhg_disk
  PV Size               203.92 MiB / not usable 3.92 MiB
  Allocatable           NO
  PE Size               4.00 MiB
  Total PE              50
  Free PE               50   <----显示完全空闲和Total PE数一致
  Allocated PE          0
  PV UUID               S2ane6-nlFG-uSNR-35NP-Yxa6-cXRb-r8E8mK

……

从卷组里把sda6删除:

[root@liuhg /]# vgreduce liuhg_disk /dev/sda6
  Removed "/dev/sda6" from volume group "liuhg_disk"

pvdisplay -m再看看吧：

  --- NEW Physical volume ---   <-----还告诉你这是一个新的PV ^_^
  PV Name               /dev/sda6
  VG Name               <-----空了
  PV Size               203.92 MiB
  Allocatable           NO
  PE Size               0  
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               S2ane6-nlFG-uSNR-35NP-Yxa6-cXRb-r8E8mK

到此vgdisplay -v能看到已经没有了/dev/sda6了。重新挂载/home

[root@liuhg /]# mount /dev/liuhg_disk/home /home
[root@liuhg /]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1             2.0G  546M  1.3G  30% /
tmpfs                 504M     0  504M   0% /dev/shm
/dev/mapper/liuhg_disk-home
                      2.2G  1.8G   42M  98% /home

进去看看数据，一个都没丢。