一、LVM是什么
LVM是 Logical Volume Manager（逻辑卷管理）的简写，简单的说LVM可以跨分区存储数据，并且LVM可以在无需停机的状态下动态调整分区的大小。
二、基本术语
*物理存储介质（PhysicalStorageMedia）
指系统的物理存储设备：磁盘，如：/dev/hda、/dev/sda等，是存储系统最底层的存储单元。
*物理卷（Physical Volume，PV）
指磁盘分区或从逻辑上与磁盘分区具有同样功能的设备（如RAID），是LVM的基本存储逻辑块，但和基本的物理存储介质（如分区、磁盘等）比较，却包含有与LVM相关的管理参数。
*卷组（Volume Group，VG）
类似于非LVM系统中的物理磁盘，其由一个或多个物理卷PV组成。可以在卷组上创建一个或多个LV（逻辑卷）。
*逻辑卷（Logical Volume，LV）
类似于非LVM系统中的磁盘分区，逻辑卷建立在卷组VG之上。在逻辑卷LV之上可以建立文件系统（比如/home或者/usr等）。
*物理块（Physical Extent，PE）
每一个物理卷PV被划分为称为PE（Physical Extents）的基本单元，具有唯一编号的PE是可以被LVM寻址的最小单元。PE的大小是可配置的，默认为4MB。所以物理卷（PV）由大小等同的基本单元PE组成。
*逻辑块（Logical Extent，LE）
每一个物理卷PV被划分为称为PE（Physical Extents）的基本单元，具有唯一编号的PE是可以被LVM寻址的最小单元。PE的大小是可配置的，默认为4MB。所以物理卷（PV）由大小等同的基本单元PE组成。
逻辑卷LV也被划分为可被寻址的基本单位，称为LE。在同一个卷组中，LE的大小和PE是相同的，并且一一对应。如图（1）
三、创建管理
常用管理命令如下：
管理lv:
pv: pvcreate, pvdisplay, pvs, pvscan, pvremove, pvmove
vg: vgcreate, vgdisplay, vgs, vgscan, vgremove, vgextend, vgreduce
lv: lvcreate, lvdisplay, lvs, lvresize, lvextend, lvreduce, lvremove
1、PV相关操作
创建pv
1.1、如图（2） 使用fdisk创建物理磁盘分区
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[root@www ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xd9180e6e
Device Boot Start
End
Blocks Id System
/dev/sdb1 1 262 2104483+ 8e Linux LVM
/dev/sdb2 263 655 3156772+ 8e Linux LVM
[root@www ~]#
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创建物理卷
pvcreate
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[root@www ~]# pvcreate /dev/sdb1 /dev/sdb2
//创建PV
Physical volume
"/dev/sdb1"
successfully created
Physical volume
"/dev/sdb2"
successfully created
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查看PV
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[root@www ~]# pvs
//查看PV
PV VG Fmt Attr PSize PFree
/dev/sda2 vg0 lvm2 a-- 59.99g 7.99g
/dev/sdb1 lvm2 --- 2.01g 2.01g
/dev/sdb2 lvm2 --- 3.01g 3.01g
[root@www ~]# pvdisplay /dev/sdb[0-9]
//可以看到详细信息
--- Physical volume ---
PV Name /dev/sdb1
VG Name myvg
PV Size 2.01 GiB / not usable 3.16 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 513
Free PE 513
Allocated PE 0
PV UUID rA5Vdy-j2rr-b9Vf-zo8I-sjFD-1z23-VhHAgI
--- Physical volume ---
PV Name /dev/sdb2
VG Name myvg
PV Size 3.01 GiB / not usable 2.79 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 770
Free PE 770
Allocated PE 0
PV UUID GVtLyK-Ugd1-DKHo-3wHS-oia1-lbpz-PA4oma
[root@www ~]#
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删除pv
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[root@www ~]# pvcreate /dev/sdb3
//创建pv
Physical volume
"/dev/sdb3"
successfully created
[root@www ~]# pvs
//查看pv
PV VG Fmt Attr PSize PFree
/dev/sda2 vg0 lvm2 a-- 59.99g 7.99g
/dev/sdb1 myvg lvm2 a-- 2.00g 0
/dev/sdb2 myvg lvm2 a-- 3.01g 2.01g
/dev/sdb3 lvm2 --- 3.01g 3.01g
[root@www ~]# pvremove /dev/sdb3
//删除pv /dev/sdb3
Labels on physical volume
"/dev/sdb3"
successfully wiped
[root@www ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg0 lvm2 a-- 59.99g 7.99g
/dev/sdb1 myvg lvm2 a-- 2.00g 0
/dev/sdb2 myvg lvm2 a-- 3.01g 2.01g
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2、VG相关操作
创建VG
vgcreate
# vgcreate VGNAME /dev/PV1...
[-s|--physicalextentsize PhysicalExtentSize[bBsSkKmMgGtTpPeE]] //指定PE大小
[-t|--test] //测试，不真正创建
[-v|--verbose]//显示创建过程
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[root@www ~]# vgcreate myvg /dev/sdb{1,2}
Volume group
"myvg"
successfully created
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查看VG
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[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
myvg 2 0 0 wz--n- 5.01g 5.01g
vg0 1 4 0 wz--n- 59.99g 7.99g
[root@www ~]# vgdisplay
--- Volume group ---
VG Name myvg
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size 5.01 GiB
PE Size 4.00 MiB
//PE 块大小
Total PE 1283
Alloc PE / Size 0 / 0
Free PE / Size 1283 / 5.01 GiB
VG UUID llSGpO-Bk51-KVBB-llAZ-AA9E-aBYq-sUrnPL
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删除vg
# vgremove VGNAME...
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[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
myvg 2 0 0 wz--n- 5.01g 5.01g
vg0 1 4 0 wz--n- 59.99g 7.99g
[root@www ~]# vgremove myvg
//删除vg
Volume group
"myvg"
successfully removed
[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
vg0 1 4 0 wz--n- 59.99g 7.99g
[root@www ~]#
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缩减VG：通过从vg中移除pv实现
注意：计划移除的pv不能包含已经存储数据的pe；如果有需要先使用pvmove移动到同vg内其它pv上；
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[root@www ~]# vgcreate myvg /dev/sdb{1,2}
Volume group
"myvg"
successfully created
[root@www ~]# vgdisplay
--- Volume group ---
VG Name myvg
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size 5.01 GiB
//大小为5G
PE Size 4.00 MiB
Total PE 1283
Alloc PE / Size 0 / 0
Free PE / Size 1283 / 5.01 GiB
VG UUID Iz9bc0-Sw38-H916-TAg3-abNh-iUJW-hjuRoB
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------------------------------------------------------------------------------
我们要在myvg中移除/dev/sdb2 【缩减vg要保证缩减后的vg大小能够存储原来的数据】
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[root@www ~]# pvmove /dev/sdb2
// 将/sdb2中的数据移动到其他pv上
No data to move
for
myvg
[root@www ~]# vgreduce myvg /dev/sdb2
//移除/dev/sdb2
Removed
"/dev/sdb2"
from volume group
"myvg"
[root@www ~]# vgdisplay myvg
--- Volume group ---
VG Name myvg
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 2
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 1
Act PV 1
VG Size 2.00 GiB
// 大小变为2G
PE Size 4.00 MiB
Total PE 513
Alloc PE / Size 0 / 0
Free PE / Size 513 / 2.00 GiB
VG UUID Iz9bc0-Sw38-H916-TAg3-abNh-iUJW-hjuRoB
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-----------------------
扩展VG： 向VG中添加更多的PV来实现
vgextend
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[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
myvg 1 0 0 wz--n- 2.00g 2.00g
//扩展前大小为2G
vg0 1 4 0 wz--n- 59.99g 7.99g
[root@www ~]# vgextend myvg /dev/sdb2
//向myvg中添加/dev/sdb2
Volume group
"myvg"
successfully extended
[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
myvg 2 0 0 wz--n- 5.01g 5.01g
//大小变为5G
vg0 1 4 0 wz--n- 59.99g 7.99g
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3、LV相关操作
创建LV Logical Volume
创建lv:
lvcreate -L #[bBsSkKmMgGtTpPeE] [-n|--name LogicalVolume{Name|Path}] VG_NAME
LV设备路径：
(1) /dev/VGNAME/LVNAME
(2) /dev/mapper/VGNAME-LVNAME
实际路径：/dev/dm-#
注意：lv的大小必须为pe的整数倍
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[root@www ~]# lvcreate -L 4G -n mylv myvg
//创建大小为4G的LV 名字为mylv
Logical volume
"mylv"
created
[root@www ~]# lvs
//查看LV
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 4.00g
//大小为4G
root vg0 -wi-ao---- 20.00g
swap vg0 -wi-ao---- 2.00g
usr vg0 -wi-ao---- 10.00g
var
vg0 -wi-ao---- 20.00g
[root@www ~]# lvdisplay
--- Logical volume ---
LV Path /dev/myvg/mylv
LV Name mylv
VG Name myvg
LV UUID i3tDAL-GdB4-TVIf-Efun-vVmg-Ig00-cSCdKk
LV Write Access read/write
LV Creation host, time www.w1.com, 2015-08-16 05:05:40 +0800
LV Status available
# open 0
LV Size 4.00 GiB
Current LE 1024
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
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移除LV
lvremove LV_PATH
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[root@www ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 4.00g
//查看lv
root vg0 -wi-ao---- 20.00g
swap vg0 -wi-ao---- 2.00g
usr vg0 -wi-ao---- 10.00g
var
vg0 -wi-ao---- 20.00g
[root@www ~]# lvremove /dev/myvg/mylv
//移除mylv
Do you really want to remove active logical volume mylv? [y/n]: y
Logical volume
"mylv"
successfully removed
[root@www ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
root vg0 -wi-ao---- 20.00g
//已经不存在mylv
swap vg0 -wi-ao---- 2.00g
usr vg0 -wi-ao---- 10.00g
var
vg0 -wi-ao---- 20.00g
[root@www ~]#
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扩展LV
存储设备有：物理边界
文件系统有：逻辑边界
扩展：先扩展物理边界，而后拉伸逻辑边界
lvextend, lvresize
resize2fs
扩展LV步骤
1、先确定目标大小：要确保此lv所在vg中有足够的空闲可用；
2G --> 4G
4G
+2G
2、扩展物理边界
lvextend -L [+]#[bBsSkKmMgGtTpPeE] /dev/VGNAME/LVNAME
3、拉伸逻辑边界
resize2fs /dev/VGNAME/LVNAME
例：先创建大小为2G的LV然后在扩展为4G
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[root@www ~]# lvcreate -L 2G -n mylv myvg
Logical volume
"mylv"
created
[root@www ~]# lvdisplay /dev/myvg/mylv
--- Logical volume ---
LV Path /dev/myvg/mylv
LV Name mylv
VG Name myvg
LV UUID yZE2SK-G9J9-dFdH-uJvK-Lln6-AS2G-UqHMjU
LV Write Access read/write
LV Creation host, time www.w1.com, 2015-08-16 05:12:04 +0800
LV Status available
# open 0
LV Size 2.00 GiB
Current LE 512
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
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格式化/myvg/mylv
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[root@www ~]# mke2fs -t ext4 /dev/myvg/mylv
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
131072 inodes, 524288 blocks
26214 blocks (5.00%) reserved
for
the super user
First data block=0
Maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks
and
filesystem accounting information: done
This filesystem will be automatically checked every 38 mounts
or
180 days, whichever comes first. Use tune2fs -c
or
-i to override.
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[root@www ~]#
mkdir
/nyist
//创建挂载点
[root@www ~]# mount /dev/myvg/mylv /nyist
//挂载
[root@www ~]# df -h
//查看大小
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-root 20G 18G 908M 96% /
tmpfs 565M 0 565M 0% /dev/shm
/dev/sda1 190M 33M 148M 18% /boot
/dev/mapper/vg0-usr 9.8G 2.4G 6.9G 26% /usr
/dev/mapper/vg0-
var
20G 294M 19G 2% /
var
/dev/sda3 59G 4.7G 52G 9% /usr/soc
/dev/mapper/myvg-mylv
2.0G 3.0M 1.9G 1% /nyist
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[root@www ~]# cp /etc/fstab /nyist
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查看文件
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[root@www ~]# cat /nyist/fstab
#
# /etc/fstab
# Created by anaconda on Thu Mar 26 20:01:38 2015
#
# Accessible filesystems, by reference, are maintained under
'/dev/disk'
# See man pages fstab(5), findfs(8), mount(8)
and
/
or
blkid(8)
for
more info
#
/dev/mapper/vg0-root / ext4 defaults 1 1
UUID=0d0698ff-1645-4ff8-af27-fc6e73573941 /boot ext4 defaults 1 2
/dev/mapper/vg0-usr /usr ext4 defaults 1 2
/dev/mapper/vg0-
var
/
var
ext4 defaults 1 2
/dev/mapper/vg0-swap swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
/dev/sda3 /usr/soc ext4 defaults 0 0
[root@www ~]#
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查看VG剩余空间：
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[root@www ~]# vgs
VG #PV #LV #SN Attr VSize VFree
myvg 2 1 0 wz--n- 5.01g 3.01g
//还有3G 我们要扩展到4G 容量足够
vg0 1 4 0 wz--n- 59.99g 7.99g
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扩展物理边界
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[root@www ~]# lvs /dev/myvg/mylv
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 2.00g //目前大小为2G
[root@www ~]# lvextend -L 4G /dev/myvg/mylv //扩展LV 也可以写为： lvextend -L +2G /vev/myvg/mylv
Size of logical volume myvg/mylv changed from 2.00 GiB (512 extents) to 4.00 GiB (1024 extents).
Logical volume mylv successfully resized
[root@www ~]# lvs /dev/myvg/mylv查看mylv大小
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 4.00g //扩展为4G
[root@www ~]#
[root@www ~]# lvdisplay /dev/myvg/mylv
--- Logical volume ---
LV Path /dev/myvg/mylv
LV Name mylv
VG Name myvg
LV UUID yZE2SK-G9J9-dFdH-uJvK-Lln6-AS2G-UqHMjU
LV Write Access read/write
LV Creation host, time www.w1.com, 2015-08-16 05:12:04 +0800
LV Status available
# open 0
LV Size 4.00 GiB //已经扩展为4G
Current LE 1024
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:4
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查看逻辑空间大小
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[root@www ~]# df -h
Filesystem Size Used Avail Use% Mounted on
......
/dev/sda3 59G 4.7G 52G 9% /usr/soc
/dev/mapper/myvg-mylv
2.0G 3.1M 1.9G 1% /nyist
//依然为2G
[root@www ~]#
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拉伸逻辑边界
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[root@www ~]# resize2fs /dev/myvg/mylv
//扩展逻辑边界
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/myvg/mylv is mounted on /nyist; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/myvg/mylv to 1048576 (4k) blocks.
The filesystem on /dev/myvg/mylv is now 1048576 blocks long.
[root@www ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-root 20G 18G 908M 96% /
tmpfs 565M 0 565M 0% /dev/shm
/dev/sda1 190M 33M 148M 18% /boot
/dev/mapper/vg0-usr 9.8G 2.4G 6.9G 26% /usr
/dev/mapper/vg0-
var
20G 294M 19G 2% /
var
/dev/sda3 59G 4.7G 52G 9% /usr/soc
/dev/mapper/myvg-mylv
3.9G 4.0M 3.7G 1% /nyist
//大小已经为3.9G 成功扩展
[root@www ~]#
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============================================================
缩减LV
注意：
1、缩减LV必须要离线
2、必须先缩减文件系统，然后再缩减LV大小
过程：
1、先确定缩减后的目标大小：要确保缩减后的大小能够容纳现在的所有数据；
2、卸载逻辑卷，并强制做文件系统一致性检查；
e2fsck -f /dev/VGNAME/LVNAME
3、缩减逻辑边界
resize2fs /dev/VGNAME/LVNAME #[bBsSkKmMgGtTpPeE]
// resize2fs /dev/myvg/mylv 3G
4、缩减物理边界
lvreduce -L [-]#[bBsSkKmMgGtTpPeE] /dev/VGNAME/LVNAME
//lvreduce -L 3G /dev/myvg/mylv //缩减到3G
eg:
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[root@www ~]# umount /nyist
[root@www ~]# e2fsck -f /dev/myvg/mylv
e2fsck 1.41.12 (17-May-2010)
Pass 1: Checking inodes, blocks,
and
sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/myvg/mylv: 12/262144 files (0.0% non-contiguous), 33871/1048576 blocks
[root@www ~]# resize2fs /dev/myvg/mylv 3G
//缩减逻辑边界
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/myvg/mylv to 786432 (4k) blocks.
The filesystem on /dev/myvg/mylv is now 786432 blocks long.
[root@www ~]# lvreduce -L 3G /dev/myvg/mylv
//缩减物理边界
WARNING: Reducing active logical volume to 3.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce mylv? [y/n]: y
Size of logical volume myvg/mylv changed from 4.00 GiB (1024 extents) to 3.00 GiB (768 extents).
Logical volume mylv successfully resized
[root@www ~]#
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验证：
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[root@www ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
mylv myvg -wi-a----- 3.00g
//大小3G
root vg0 -wi-ao---- 20.00g
swap vg0 -wi-ao---- 2.00g
usr vg0 -wi-ao---- 10.00g
var
vg0 -wi-ao---- 20.00g
[root@www ~]# mount /dev/myvg/mylv /nyist
[root@www ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-root 20G 18G 908M 96% /
tmpfs 565M 0 565M 0% /dev/shm
/dev/sda1 190M 33M 148M 18% /boot
/dev/mapper/vg0-usr 9.8G 2.4G 6.9G 26% /usr
/dev/mapper/vg0-
var
20G 294M 19G 2% /
var
/dev/sda3 59G 4.7G 52G 9% /usr/soc
/dev/mapper/myvg-mylv
2.9G 3.1M 2.8G 1% /nyist
//大小2.9G
[root@www ~]#
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本文转自 1inux 51CTO博客，原文链接:http://blog.51cto.com/1inux/1706105
