在linux中减小和增大LV的过程与思考

今天在安装oracle 11 rac的时候，查看操作系统df -lh,发现/home目录竟然分了500多G，/根目录才有50G，当时我就爆了句粗口，这TM系统是怎么做的。

Filesystem                              Size     Used    Avail   Use% Mounted on

/dev/mapper/vg_db5-lv_root                 50G     6.2G   41G   14%    /

tmpfs                                      127G    84K  127G    1%     /dev/shm

/dev/sdq1                                  477M    37M  415M    9%     /boot

/dev/mapper/vg_db5-lv_home                 496G    70M  471G    1%     /home

#vgdisplay

--- Volume group ---

VG Name               vg_db5

System ID

Format                lvm2

Metadata Areas        1

Metadata Sequence No  4

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               557.26 GiB

PE Size               4.00 MiB

Total PE              142658

Alloc PE / Size       142658 / 557.26 GiB

Free  PE / Size       0 / 0

VG UUID               plc2K9-lRVy-bcck-B9Qp-3F8k-H6cW-W4vRdS

#lvdisplay

--- Logical volume ---

LV Path                /dev/vg_db6/lv_root

LV Name                lv_root

VG Name                vg_db6

LV UUID                6HlVnp-6RGm-kORQ-eOx6-nQQV-8PWB-Gg4WNE

LV Write Access        read/write

LV Creation host, time db6, 2015-02-02 19:25:11 +0800

LV Status              available

# open                 1

LV Size                50.00 GiB

Current LE             12800

Segments               1

Allocation             inherit

Read ahead sectors     auto

- currently set to     256

Block device           253:0

--- Logical volume ---

LV Path                /dev/vg_db6/lv_home

LV Name                lv_home

VG Name                vg_db6

LV UUID                yuBJai-96D6-JFwX-cmXR-EeXE-cUuU-uqRl3l

LV Write Access        read/write

LV Creation host, time db6, 2015-02-02 19:25:17 +0800

LV Status              available

# open                 1

LV Size                503.26 GiB

Current LE             128834

Segments               1

Allocation             inherit

Read ahead sectors     auto

- currently set to     256

Block device           253:10

--- Logical volume ---

LV Path                /dev/vg_db6/lv_swap

LV Name                lv_swap

VG Name                vg_db6

LV UUID                d5FqB1-tTHM-HSrb-b0tm-r1Ms-XnvP-dH5ovs

LV Write Access        read/write

LV Creation host, time db6, 2015-02-02 19:27:23 +0800

LV Status              available

# open                 1

LV Size                4.00 GiB

Current LE             1024

Segments               1

Allocation             inherit

Read ahead sectors     auto

- currently set to     256

Block device           253:1

有三个lv在一个VG里，决定把这三个LV的大小给调整一下。把lv_home调小,然后把lv_root调大。注意，缩小空间是有风险的，所以我先把里面的oracle,grid用户还有所有的组都删除了，然后重启系统。

#userdel oracle

#userdel grid

#groudel  oinstall

....................

重启之后，查看/etc/group,/etc/passwd,确认没有用户和组了，我们就可以开始了。

1.#umount /home1.#umount /home

如果不成功，可能会报错，解决方法如下：umount: /mnt/cdrom: device is busy.

(In some cases useful info about processes that

use the device is found by lsof(8) or user(1))

#umount /mnt/cdrom/ -f    //强制卸载也不行

umount2: 设备或资源忙

umount: /mnt: device is busy.

(In some cases useful info about processes that use

the device is found by lsof(8) or fuser(1))umount2: 设备或资源忙

#fuser -m /home

/home:          1338c

# ps aux |grep 1338

root      1338  0.0  0.2 108292  1912 pts/2    Ss+  14:27   0:00 -bash

root      1423  0.0  0.1 103236   884 pts/1    S+   14:49   0:00 grep 1338

#kill -9 1338

#fuser -m /home

#umount /home

解析：不过感觉这种方法也只是用于那些无关紧要的目录，因为进程使用的少，如果是/目录，可能进程会杀不过来，杀完了，系统估计也崩了。

逻辑卷的缩减，有风险，先缩减逻辑边界——在缩减物理边界

注意：       1、不能在线缩减，得先卸载；

2、确保缩减后的空间大小依然能存储原有的所有数据；

3、在缩减之前应该强行检查文件，确保文件系统处于一致性状态

2. 检查一下

#e2fsck -f /dev/vg_db5/lv_home

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/vg_db5/lv_home: 29/32989184 files (0.0% non-contiguous), 2121120/131926016 blocks

3.开始缩小文件系统：

#resize2fs /dev/vg_db5/lv_home 1024M

resize2fs 1.41.12 (17-May-2010)

resize2fs: New size smaller than minimum (307344)

显示1G太小了，最小是307344个块。得了，10个G吧

#resize2fs /dev/vg_db5/lv_home 10G

resize2fs 1.41.12 (17-May-2010)

Resizing the filesystem on /dev/vg_db5/lv_home to 2621440 (4k) blocks.

The filesystem on /dev/vg_db5/lv_home is now 2621440 blocks long.

4.缩小lv大小：

# lvreduce -L 10G /dev/vg_db5/lv_home

WARNING: Reducing active logical volume to 10.00 GiB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce lv_home? [y/n]: y

Size of logical volume vg_db5/lv_home changed from 503.26 GiB (128834 extents) to 10.00 GiB (2560 extents).

Logical volume lv_home successfully resized

#vgdisplay  发现空间已经释放出来了

--- Volume group ---

VG Name               vg_db5

System ID

Format                lvm2

Metadata Areas        1

Metadata Sequence No  5

VG Access             read/write

VG Status             resizable

MAX LV                0

Cur LV                3

Open LV               2

Max PV                0

Cur PV                1

Act PV                1

VG Size               557.26 GiB

PE Size               4.00 MiB

Total PE              142658

Alloc PE / Size       16384 / 64.00 GiB

Free  PE / Size       126274 / 493.26 GiB

VG UUID               Ji4TQc-IbhS-O6Cb-XH5Q-q4Uk-DIer-DvSMMD

5.增大LV：lv_root 的大小，增大到500G

#lvextend -L  500G -f -r /dev/vg_db5/lv_root

Size of logical volume vg_db5/lv_root changed from 50.00 GiB (12800 extents) to 500.00 GiB (128000 extents).

Logical volume lv_root successfully resized

resize2fs 1.41.12 (17-May-2010)

Filesystem at /dev/mapper/vg_db5-lv_root is mounted on /; on-line resizing required

old desc_blocks = 4, new_desc_blocks = 32

Performing an on-line resize of /dev/mapper/vg_db5-lv_root to 131072000 (4k) blocks.

The filesystem on /dev/mapper/vg_db5-lv_root is now 131072000 blocks long.

想再增加操作系统大小，看来不用做了。

# resize2fs /dev/vg_db5/lv_root 500G

resize2fs 1.41.12 (17-May-2010)

The filesystem is already 131072000 blocks long.  Nothing to do!

#resize2fs -p /dev/vg_db5/lv_root

resize2fs 1.41.12 (17-May-2010)

The filesystem is already 131072000 blocks long.  Nothing to do!

重启之后：

#df -lh

Filesystem                             Size     Used   Avail   Use% Mounted on

/dev/mapper/vg_db5-lv_root                493G  6.2G    461G   2%            /

tmpfs                                     160G  144K    160G   1%            /dev/shm

/dev/sdq1                                 477M   37M  415M   9% /boot

/dev/mapper/vg_db5-lv_home                9.8G   37M  9.2G   1% /home

终于搞定了。

更为详细的LVM的理论概念请参见博客：

http://80cto.blog.51cto.com/7503144/1610922