LVM 逻辑卷管理，lvm逻辑卷

文章由LinuxBoy分享于2019-04-03 05:04:06热评（347）

LVM 逻辑卷管理，lvm逻辑卷

简介：

LVM ( Logical Volume Manager ) 逻辑卷管理

一、创建 LV

1、首先在你的虚拟机上添加一块新的硬盘用来做实验。

2、安装 lvm : yum -y install lvm2

3、查看新添加的磁盘

shell > fdisk -l

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: 0x00000000

## 其中，/dev/sdb 就是我新添加的磁盘了

4、创建物理分区

shell > fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x62beb6a4.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.

Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

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                          # 帮助信息
Command action
        a toggle a bootable flag
        b edit bsd disklabel
        c toggle the dos compatibility flag
        d delete a partition                     # 删除一个分区
        l list known partition types             # 打印分区类型对应的 ID 号
        m print this menu
        n add a new partition                    # 添加一个分区
        o create a new empty DOS partition table
        p print the partition table              # 打印分区表
        q quit without saving changes            # 不保存退出
        s create a new empty Sun disklabel
        t change a partition's system id         # 更改分区 ID
        u change display/entry units
        v verify the partition table
        w write table to disk and exit           # 保存退出
        x extra functionality (experts only)

## 执行的命令是 fdisk /dev/sdb .

Command (m for help): n                          # 执行添加分区指令
Command action
e extended
p primary partition (1-4)
p                                                # 添加一个主分区
Partition number (1-4): 1                        # 分区号为 1
First cylinder (1-2610, default 1):              # 分区起始位置（直接回车）
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-2610, default 2610): +1024M   # 分区结束位置(+1024M 表示 1G 大小)

Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (133-2610, default 133):
Using default value 133
Last cylinder, +cylinders or +size{K,M,G} (133-2610, default 2610): +1024M

Command (m for help): p                          # 执行打印分区表

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: 0x62beb6a4

Device Boot Start End Blocks Id System
/dev/sdb1 1 132 1060258+ 83 Linux
/dev/sdb2 133 264 1060290 83 Linux

## 可以看到分了两个区 /dev/sdb1 /dev/sdb2

Command (m for help): t                          # 执行更改分区 ID （83 表示Linux 普通分区、82 表示swap、8e 表示LVM）
Partition number (1-4): 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)

Command (m for help): t
Partition number (1-4): 2
Hex code (type L to list codes): 8e
Changed system type of partition 2 to 8e (Linux LVM)

Command (m for help): p

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: 0x62beb6a4

Device Boot Start End Blocks Id System
/dev/sdb1 1 132 1060258+ 8e Linux LVM
/dev/sdb2 133 264 1060290 8e Linux LVM

## 已经看到分区 ID 变为 8e ; 文件系统为 Linux LVM

Command (m for help): w                          # 执行保存退出
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

shell > 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: 0x62beb6a4

Device Boot Start End Blocks Id System
/dev/sdb1 1 132 1060258+ 8e Linux LVM
/dev/sdb2 133 264 1060290 8e Linux LVM

## 可以看到磁盘 /dev/sdb 有两个分区 /dev/sdb1 /dev/sdb2

5、创建 PV （物理卷）

shell > pvcreate /dev/sdb1 /dev/sdb2
  Physical volume "/dev/sdb1" successfully created
  Physical volume "/dev/sdb2" successfully created

## 使用 pvcreate 创建 PV 后面跟想要创建的分区

shell > pvscan
  PV /dev/sda3 VG vg_study lvm2 [18.80 GiB / 0 free]
  PV /dev/sdb1 lvm2 [1.01 GiB]
  PV /dev/sdb2 lvm2 [1.01 GiB]
  Total: 3 [20.82 GiB] / in use: 1 [18.80 GiB] / in no VG: 2 [2.02 GiB]

## 使用 pvscan 、pvdisplay 、pvs 都可以查看 PV
## PV /dev/sdb1 pv /dev/sdb2 为我新创建的 PV 大小为 1G（PV /dev/sda3 为之前创建的属 VG vg_study ）

6、创建 VG （卷组）

shell > vgcreate my_vg /dev/sdb1 /dev/sdb2
  Volume group "my_vg" successfully created

## 使用 vgcreate 创建卷组，后面接 vg 名，接 pv

shell > vgdisplay
  --- Volume group ---
  VG Name my_vg
  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 2.02 GiB
  PE Size 4.00 MiB
  Total PE 516
  Alloc PE / Size 0 / 0
  Free PE / Size 516 / 2.02 GiB
  VG UUID ynCJG8-ZIvI-9gBF-dO5K-aQws-N9WW-r26hch

## 同样可以使用 vgscan 、vgs 、vgdisplay 来查看 VG
## 可以看到 VG名为 my_vg 、VG 大小为 2G 、PE 大小 4M 等

7、创建 LV （逻辑卷）

shell > lvcreate -L 2G -n my_lv my_vg
  Logical volume "my_lv" created

## 使用 lvcreate 创建 LV ，-L 指定 LV大小，-n 指定 LV名称，后面接 VG名

shell > lvdisplay
  --- Logical volume ---
  LV Path /dev/my_vg/my_lv
  LV Name my_lv
  VG Name my_vg
  LV UUID j9Bduh-3TB9-Owhz-X3PX-fVeQ-bvJe-OAFBVp
  LV Write Access read/write
  LV Creation host, time study.localhost.localdomain, 2014-11-26 11:14:28 +0800
  LV Status available
  # open 0
  LV Size 2.00 GiB
  Current LE 512
  Segments 2
  Allocation inherit
  Read ahead sectors auto
  - currently set to 256
  Block device 253:1

## 同样可以使用 lvscan 、lvs 、lvdisplay 来查看 LV
## 可以看到 LV路径 /dev/my_vg/my_lv 、LV名 my_lv 、VG名 my_vg 、LV大小 2G 等

8、创建文件系统（格式化）

shell > mkfs.ext4 /dev/my_vg/my_lv
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
131072 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
第一个数据块=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

正在写入inode表: 完成
Creating journal (16384 blocks): 完成
Writing superblocks and filesystem accounting information: 完成

This filesystem will be automatically checked every 32 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.

## 使用 mkfs.ext4 格式化为 ext4 文件系统

9、挂载使用

shell > mkdir /data
shell > mount /dev/my_vg/my_lv /data/
shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.4G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 2.2G 71M 2.0G 4% /data

## 创建 /data 目录，将 /dev/my_vg/my_lv 挂载到 /data

shell > umount /data/
shell > blkid /dev/my_vg/my_lv
/dev/my_vg/my_lv: UUID="a8cb322e-1872-4ea8-bfba-f21b678bc849" TYPE="ext4"
shell > echo "UUID="a8cb322e-1872-4ea8-bfba-f21b678bc849" /data ext4 defaults 0 0" >> /etc/fstab
shell > mount -a
shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.5G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 2.2G 71M 2.0G 4% /data

## 也可以使用 blkid 生成 UUID 然后写入到 /etc/fstab 文件中，实现开机自动挂载

二、扩容 LV

1、首先创建物理分区（重点是这次创建后要格式化）

2、创建 PV

3、扩容 VG

shell > vgextend my_vg /dev/sdb3
  Volume group "my_vg" successfully extended

## 使用 vgextend 指令扩展 VG ，后面接要扩展的 VG名，后面接将哪个 PV 扩展进去

shell > vgdisplay my_vg
  --- Volume group ---
  VG Name my_vg
  System ID
  Format lvm2
  Metadata Areas 3
  Metadata Sequence No 3
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 1
  Open LV 1
  Max PV 0
  Cur PV 3
  Act PV 3
  VG Size 3.02 GiB
  PE Size 4.00 MiB
  Total PE 774
  Alloc PE / Size 512 / 2.00 GiB
  Free PE / Size 262 / 1.02 GiB
  VG UUID ynCJG8-ZIvI-9gBF-dO5K-aQws-N9WW-r26hch

## 可以使用 vgdisplay my_vg 来指定查看哪个 VG
## 可以看到 VG 总大小为 3G 、已使用 2G 、空闲 1G（因为我们扩进去 1G 的 PV）

4、扩容 LV

shell > lvextend -L +1G /dev/my_vg/my_lv
  Size of logical volume my_vg/my_lv changed from 2.00 GiB (512 extents) to 3.00 GiB (768 extents).
  Logical volume my_lv successfully resized

## 使用 lvextend 扩容 LV ，-L 指定扩多大，后面接 LV 实际路径 /dev/my_vg/my_lv

shell > lvdisplay /dev/my_vg/my_lv
  --- Logical volume ---
  LV Path /dev/my_vg/my_lv
  LV Name my_lv
  VG Name my_vg
  LV UUID j9Bduh-3TB9-Owhz-X3PX-fVeQ-bvJe-OAFBVp
  LV Write Access read/write
  LV Creation host, time study.localhost.localdomain, 2014-11-26 11:14:28 +0800
  LV Status available
  # open 1
  LV Size 3.00 GiB
  Current LE 768
  Segments 3
  Allocation inherit
  Read ahead sectors auto
  - currently set to 256
  Block device 253:1

## 可以使用 lvdisplay /dev/my_vg/my_lv 来查看 LV 大小
## LV 大小变为了 3G （原 2G）

5、投入使用

shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.4G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 2.2G 71M 2.0G 4% /data

## 我们发现分区 /data 大小还是 2G

shell > resize2fs /dev/my_vg/my_lv
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/my_vg/my_lv is mounted on /data; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/my_vg/my_lv to 786432 (4k) blocks.
The filesystem on /dev/my_vg/my_lv is now 786432 blocks long.

shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.4G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 3.2G 71M 3.0G 3% /data

## 使用 resize2fs /dev/my_vg/my_lv 重新计算分区大小后发现扩容到了 3G

三、缩减 LV

1、模拟数据写入

shell > dd if=/dev/zero of=/data/block.db bs=1024M count=1
记录了1+0 的读入
记录了1+0 的写出
1073741824字节(1.1 GB)已复制，81.6381 秒，13.2 MB/秒

## 我们使用 dd 命令写了 1G 的数据到 /data

shell > cp /etc/passwd /data/ ## 复制这个文件的目的是验证数据是否丢失

shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.4G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 3.2G 1.2G 1.9G 39% /data

## 现在这个剩余空间我们想把他撤出来 1G

2、首先检查一下文件系统

shell > umount /data/ ## 一定要先 umount
shell > e2fsck -f /dev/my_vg/my_lv
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/my_vg/my_lv: 13/196608 files (0.0% non-contiguous), 291646/786432 blocks

3、重新计算大小

shell > resize2fs /dev/my_vg/my_lv 2G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/my_vg/my_lv to 524288 (4k) blocks.
The filesystem on /dev/my_vg/my_lv is now 524288 blocks long.

## 重新定义大小为 2G

4、缩小 LV

shell > lvreduce -L -1G /dev/my_vg/my_lv
  WARNING: Reducing active logical volume to 2.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
  Do you really want to reduce my_lv? [y/n]: y
  Size of logical volume my_vg/my_lv changed from 3.00 GiB (768 extents) to 2.00 GiB (512 extents).
  Logical volume my_lv successfully resized

## 使用 lvreduce 来缩小 LV ，-L -1G 缩小 1G

shell > mount -a
shell > df -HT
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/vg_study-LogVol00 ext4 20G 1.4G 18G 8% /
tmpfs tmpfs 521M 0 521M 0% /dev/shm
/dev/sda1 ext4 204M 30M 164M 16% /boot
/dev/mapper/my_vg-my_lv ext4 2.2G 1.2G 863M 58% /data

shell > ls /data/
block.db lost+found passwd

## 重新挂载分区，发现数据没有问题（仅是测试，没有发现问题）

5、VG 中移除 PV

shell > vgdisplay my_vg
  --- Volume group ---
  VG Name my_vg
  System ID
  Format lvm2
  Metadata Areas 3
  Metadata Sequence No 6
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 1
  Open LV 1
  Max PV 0
  Cur PV 3
  Act PV 3
  VG Size 3.02 GiB
  PE Size 4.00 MiB
  Total PE 774
  Alloc PE / Size 637 / 2.49 GiB
  Free PE / Size 137 / 548.00 MiB
  VG UUID ynCJG8-ZIvI-9gBF-dO5K-aQws-N9WW-r26hch

## 首先我们 vgdisplay my_vg ，发现 VG 空闲 548M

shell > pvdisplay
  --- Physical volume ---
  PV Name /dev/sdb1
  VG Name my_vg
  PV Size 1.01 GiB / not usable 3.41 MiB
  Allocatable yes (but full)
  PE Size 4.00 MiB
  Total PE 258
  Free PE 0
  Allocated PE 258
  PV UUID JB8X8v-jBPU-eOiN-aEOU-TOig-tv01-SuHytd

  --- Physical volume ---
  PV Name /dev/sdb2
  VG Name my_vg
  PV Size 1.01 GiB / not usable 3.44 MiB
  Allocatable yes (but full)
  PE Size 4.00 MiB
  Total PE 258
  Free PE 0
  Allocated PE 258
  PV UUID YXBMJJ-RyG3-z1xa-tlw6-piaI-cTgj-SIBIlz

  --- Physical volume ---
  PV Name /dev/sdb3
  VG Name my_vg
  PV Size 1.01 GiB / not usable 3.44 MiB
  Allocatable yes
  PE Size 4.00 MiB
  Total PE 258
  Free PE 137
  Allocated PE 121
  PV UUID jSpEdJ-fxZh-LP27-rFIM-0gnO-mL2x-PpBJpK

## 其次使用 pvdisplay 查看 PV 的使用情况发现：
/dev/sdb1 PE 空闲 0
/dev/sdb2 PE 空闲 0
/dev/sdb3 PE 空闲 137 （上图显示每个 PE 为 4M ，那么 /dev/sdb3 总空闲容量=137*4 = 548M）
## 正好等于 VG 的空闲大小，而 PV /dev/sdb3 大小为 1G ，也就是说有部分空间被占用，所以无法移除该 PV

shell > vgreduce my_vg /dev/sdb3
  Physical volume "/dev/sdb3" still in use
shell > umount /data/
shell > vgreduce my_vg /dev/sdb3
  Physical volume "/dev/sdb3" still in use

## 提示正在被占用，无法移除（ umount 分区也不行）

shell > umount /data/

shell > e2fsck -f /dev/my_vg/my_lv
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/my_vg/my_lv: 14/163840 files (0.0% non-contiguous), 289591/652288 blocks

shell > resize2fs /dev/my_vg/my_lv 2G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/my_vg/my_lv to 524288 (4k) blocks.
The filesystem on /dev/my_vg/my_lv is now 524288 blocks long.

shell > lvreduce -L -500M /dev/my_vg/my_lv
  WARNING: Reducing active logical volume to 2.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
  Do you really want to reduce my_lv? [y/n]: y
  Size of logical volume my_vg/my_lv changed from 2.49 GiB (637 extents) to 2.00 GiB (512 extents).
  Logical volume my_lv successfully resized

## 我们把 LV 缩小了 500M

shell > vgdisplay my_vg
  --- Volume group ---
  VG Name my_vg
  System ID
  Format lvm2
  Metadata Areas 3
  Metadata Sequence No 9
  VG Access read/write
  VG Status resizable
  MAX LV 0
  Cur LV 1
  Open LV 0
  Max PV 0
  Cur PV 3
  Act PV 3
  VG Size 3.02 GiB
  PE Size 4.00 MiB
  Total PE 774
  Alloc PE / Size 512 / 2.00 GiB
  Free PE / Size 262 / 1.02 GiB
  VG UUID ynCJG8-ZIvI-9gBF-dO5K-aQws-N9WW-r26hch

## 现在再看 VG 大小空闲 1G

shell > pvdisplay
  --- Physical volume ---
  PV Name /dev/sdb3
  VG Name my_vg
  PV Size 1.01 GiB / not usable 3.44 MiB
  Allocatable yes
  PE Size 4.00 MiB
  Total PE 258
  Free PE 258
  Allocated PE 0
  PV UUID jSpEdJ-fxZh-LP27-rFIM-0gnO-mL2x-PpBJpK

## pvdisplay 也发现 /dev/sdb3 正好全部空闲

shell > vgreduce my_vg /dev/sdb3
  Removed "/dev/sdb3" from volume group "my_vg"

## 已经成功将 PV /dev/sdb3 从 VG my_vg 中移除

shell > vgs
  VG #PV #LV #SN Attr VSize VFree
  my_vg 2 1 0 wz--n- 2.02g 16.00m

## 使用 vgs 可以看到 vg my_vg 中包含 PV 数为 2

6、删除 PV

shell > pvremove /dev/sdb3
  Labels on physical volume "/dev/sdb3" successfully wiped

## 使用 pvremove 删除 PV /dev/sdb3

shell > pvs
  PV VG Fmt Attr PSize PFree
  /dev/sdb1 my_vg lvm2 a-- 1.01g 0
  /dev/sdb2 my_vg lvm2 a-- 1.01g 16.00m

## 使用 pvs 看到只有两个 PV 了
## 然后 fdisk /dev/sdb 将 sdb3 的 ID 改为 83 ，保存
mkfs.ext4 /dev/sdb3 ，重新挂载到目录，至此 /dev/sdb3 成为普通分区

四、删除整个 lv vg pv

shell > umount /data/
shell > lvremove /dev/my_vg/my_lv
  Do you really want to remove active logical volume my_lv? [y/n]: y
  Logical volume "my_lv" successfully removed
  shell > vgremove my_vg
  Volume group "my_vg" successfully removed
shell > pvremove /dev/sdb1
  Labels on physical volume "/dev/sdb1" successfully wiped
shell > pvremove /dev/sdb2
  Labels on physical volume "/dev/sdb2" successfully wiped

## 删除比创建容易多了 ...

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