Linux LVM逻辑卷管理

使用Linux好久了，一定会意识到一个问题，某个分区容量不够用了，想要扩容怎么办？这里就涉及到LVM逻辑卷的管理了，可以动态调整Linux分区容量。

LVM 概述#

全称Logical Volume Manager，可以动态调整磁盘容量，提高磁盘管理灵活性。

在安装CentOS 7的过程中选择自动分区时，默认就是以LVM的方案安装的系统。

但是/boot分区必须独立出来，不能基于LVM创建。

PV 物理卷#

物理卷，Physical Volume，是LVM机制的基本存储设备，通常对应一个普通分区或是整个硬盘。

创建物理卷时，会在分区或磁盘头部创建一个用于记录LVM属性的保留区块，并把存储空间分割成默认大小为4MB的基本单元（Physical Extend，PE），从而构成物理卷。

普通分区先转换分区类型为8e；整块硬盘，可以将所有的空间划分为一个主分区再做调整。

VG 卷组#

卷组，Volume Group，是由一个或多个物理卷组成的一个整体。可以动态添加、移除物理卷，创建时可以指定PE大小。

LV 逻辑卷#

逻辑卷，Logical Volume，建立在卷组之上，与物理卷没有直接关系。格式化后，即可挂载使用。

三者关系#

通过以上对三者的解释可以看出，建立LVM的过程。首先，将普通分区或整个硬盘创建为物理卷；然后，将一个或多个物理卷创建为卷组；最后，在卷组上分割不同的数据存储空间形成逻辑卷。有了逻辑卷，就可以格式化、挂载使用了。

LVM 管理#
LVM 常用命令#

PV 管理#
pvsacn#

• 扫描列出系统中所有的物理卷

-e:仅显示属于输出卷组的物理卷
-n：仅显示不属于任何卷组的物理卷

[root@localhost ~]# pvscan
  PV /dev/sda2   VG centos          lvm2 [<19.00 GiB / 0    free]
  PV /dev/sdb1                      lvm2 [<20.00 GiB]
  PV /dev/sdc1                      lvm2 [<20.00 GiB]
  Total: 3 [58.99 GiB] / in use: 1 [<19.00 GiB] / in no VG: 2 [<40.00 GiB]

pvcreate#

• 将分区或整个硬盘转换成物理卷

[root@localhost ~]# pvcreate /dev/sd{b,c}1
  Physical volume "/dev/sdb1" successfully created.
  Physical volume "/dev/sdc1" successfully created.

pvdisplay#

• 显示物理卷的详细信息

[root@localhost ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               centos
  PV Size               <19.00 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              4863
  Free PE               0
  Allocated PE          4863
  PV UUID               E4eovQ-CgPo-OSDK-75MO-BfD8-pGsP-BUlqip

  "/dev/sdb1" is a new physical volume of "<20.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb1
  VG Name
  PV Size               <20.00 GiB
  Allocatable           NO
  PE Size               0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               gR5mm3-f50o-XLTq-34GY-n6Iz-WXkQ-uMZAkJ

  "/dev/sdc1" is a new physical volume of "<20.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdc1
  VG Name
  PV Size               <20.00 GiB
  Allocatable           NO
  PE Size               0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               O2gKxa-ONts-kyXK-zZrO-3dDg-FhtI-V6GPy9

pvremove#

• 删除指定的物理卷，还原成普通分区或磁盘

TIPS：只有不属于卷组的物理卷才可以删除还原。

[root@localhost ~]# pvremove /dev/sdd1
  Labels on physical volume "/dev/sdd1" successfully wiped.

VG 管理#
vgscan#

• 扫描系统中已建立的LVM卷组

[root@localhost ~]# vgscan
  Reading volume groups from cache.
  Found volume group "class" using metadata type lvm2
  Found volume group "centos" using metadata type lvm2

vgcreate#

• 将一个或多个物理卷创建为一个卷组

-l：卷组上允许创建的最大逻辑卷数
-p：卷组中允许添加的最大物理卷数
-s：卷组上的物理卷的PE大小

[root@localhost ~]# vgcreate class /dev/sd{b,c}1
  Volume group "class" successfully created

vgdisplay#

• 显示系统中各卷组的详细信息

[root@localhost ~]# vgdisplay
  --- Volume group ---
  VG Name               class
  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               39.99 GiB
  PE Size               4.00 MiB
  Total PE              10238
  Alloc PE / Size       0 / 0
  Free  PE / Size       10238 / 39.99 GiB
  VG UUID               ZtQvGX-YOdy-U8wj-mGQs-TT1e-1PBR-dBNKAG

  --- Volume group ---
  VG Name               centos
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               <19.00 GiB
  PE Size               4.00 MiB
  Total PE              4863
  Alloc PE / Size       4863 / <19.00 GiB
  Free  PE / Size       0 / 0
  VG UUID               bLPJGb-SQQ3-KcUb-OSdo-qaMR-9hJE-MTkc7a

vgremove#

• 删除指定的卷组

TIPS：卷组下面的逻辑卷没有被挂载使用，卷组删除时会一并删除下面的逻辑卷。

[root@localhost ~]# vgremove class
  Volume group "class" successfully removed

vgextend#

• 添加新的物理卷，动态扩展卷组的磁盘空间

[root@localhost ~]# vgextend class /dev/sdd1
  Volume group "class" successfully extended

vgreduce#

• 删除卷组中的物理卷，减少卷组容量，

-a：如果命令行中没有指定要删除的物理卷，则删除所有的空物理卷。（all）

TIPS：删除啊前确保对应的物理卷没有在使用，就是下面没有逻辑卷，否则删除不了。

[root@localhost ~]# vgreduce class /dev/sdd1
  Removed "/dev/sdd1" from volume group "class"

[root@localhost ~]# vgreduce -a class
  Physical volume "/dev/sdb1" still in use
  Physical volume "/dev/sdc1" still in use
  Removed "/dev/sdd1" from volume group "class"

LV 管理#
lvscan#

• 扫描系统中已建立的LVM逻辑卷

[root@localhost ~]# lvscan
  ACTIVE            '/dev/class/stu01' [25.00 GiB] inherit
  ACTIVE            '/dev/class/stu02' [14.99 GiB] inherit
  ACTIVE            '/dev/centos/swap' [2.00 GiB] inherit
  ACTIVE            '/dev/centos/root' [<17.00 GiB] inherit

lvcreate#

• 从指定的卷组中分割空间，创建新的逻辑卷

-L：指定逻辑卷的大小，单位为KMGT
-l：指定百分比创建，如50%vg卷组的一半空间、100%free所有剩下的。
-n：指定逻辑卷的名称

[root@localhost ~]# lvcreate -L 15G -n stu01 class
  Logical volume "stu01" created.

[root@localhost ~]# lvcreate -l 100%free -n stu02 class
  Logical volume "stu02" created.

lvdisplay#

• 显示逻辑卷的详细信息

[root@localhost ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/class/stu01
  LV Name                stu01
  VG Name                class
  LV UUID                XUP7dq-IM9f-PdKk-XpDH-J1hx-kkuB-cOu3Qx
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2019-08-24 09:42:35 +0800
  LV Status              available
  # open                 0
  LV Size                25.00 GiB
  Current LE             6400
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2

  --- Logical volume ---
  LV Path                /dev/class/stu02
  LV Name                stu02
  VG Name                class
  LV UUID                P7iMC1-X0oT-6TCH-vLYj-HW2j-6QMu-rS7Jyp
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2019-08-24 09:59:30 +0800
  LV Status              available
  # open                 0
  LV Size                14.99 GiB
  Current LE             3838
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:3

  --- Logical volume ---
  LV Path                /dev/centos/swap
  LV Name                swap
  VG Name                centos
  LV UUID                NXiaXT-T6yv-ktM2-plyS-j6Hg-hkvu-1JQ2eL
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-16 17:12:19 +0800
  LV Status              available
  # open                 2
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:1

  --- Logical volume ---
  LV Path                /dev/centos/root
  LV Name                root
  VG Name                centos
  LV UUID                7FnsfT-B8xi-3vgu-8N0k-nzNn-8Rra-eoE4iC
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-16 17:12:19 +0800
  LV Status              available
  # open                 1
  LV Size                <17.00 GiB
  Current LE             4351
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

lvremove#

• 删除指定的逻辑卷

TIPS：备份数据，解挂载，删除。

[root@localhost ~]# umount /mnt/stu02/
[root@localhost ~]# lvremove /dev/class/stu02

lvextend#

• 动态扩展LVM逻辑卷的空间大小

-L：指定扩展逻辑卷的大小，单位为KMGT
-l：指定百分比扩建，如100%free所有剩下的。

[root@localhost ~]# lvextend -L +8G /dev/class/stu01
[root@localhost ~]# lvextend -L +8G /dev/class/stu02

TIPS：已挂载，使用在线调整大小，xfs使用xfs_growfs，ext4使用resize2fs。

[root@localhost ~]# xfs_growfs /dev/class/stu01
[root@localhost ~]# resize2fs /dev/class/stu02

lvreduce#

• 减少LVM逻辑卷的空间大小，

-L：指定逻辑卷的大小，单位为KMGT

TIPS：对于xfs文件系统，备份数据，解挂载，减少空间，强制格式化，重新挂载。需要注意xfs文件系统只能扩大，不能缩小，非要缩小的话，只有缩小后并强制格式化，但这么做数据就丢失了。

[root@localhost ~]# umount /mnt/stu01/
[root@localhost ~]# lvreduce -L -10G /dev/class/stu01
[root@localhost ~]# mkfs.xfs -f /dev/class/stu01
[root@localhost ~]# mount -a
[root@localhost ~]# df -hT

TIPS：对于ext4这类文件系统，备份数据，解挂载，e2fsck -f检查文件系统完整性，resize2fs设置文件系统大小，lvreduce设置逻辑卷大小，重新挂载。

[root@localhost ~]# umount /mnt/stu02/
[root@localhost ~]# e2fsck -f /dev/class/stu02
[root@localhost ~]# resize2fs /dev/class/stu02 10G
[root@localhost ~]# lvreduce -L 10G /dev/class/stu02
[root@localhost ~]# mount -a
[root@localhost ~]# df -hT

LVM 实验#
创建 LVM 逻辑卷#

1.添加两块20G的磁盘，重启机器，并对其进行分区，全部空间分为一个主分区，类型改为Linux LVM，ID为8e。分区过程省略，不清楚可参考上一篇博客。

[root@localhost ~]# fdisk -l /dev/sd{b,c} | grep -i "linux lvm"
/dev/sdb1            2048    41943039    20970496   8e  Linux LVM
/dev/sdc1            2048    41943039    20970496   8e  Linux LVM

2.将/dev/sdb1、/dev/sdc1转换为物理卷。

[root@localhost ~]# pvcreate /dev/sd{b,c}1
  Physical volume "/dev/sdb1" successfully created.
  Physical volume "/dev/sdc1" successfully created.

3.创建名称为class的卷组，并将sdb1和sdc1添加进卷组。

[root@localhost ~]# vgcreate class /dev/sd{b,c}1
  Volume group "class" successfully created

4.划分大小为15G，名称为stu01的逻辑卷，然后再扩容10G；剩下的空间创建名称为stu02的逻辑卷。

[root@localhost ~]# lvcreate -L 15G -n stu01 class
  Logical volume "stu01" created.
[root@localhost ~]# lvextend -L +10G /dev/class/stu01
  Size of logical volume class/stu01 changed from 15.00 GiB (3840 extents) to 25.00 GiB (6400 extents).
  Logical volume class/stu01 successfully resized.

[root@localhost ~]# lvcreate -l 100%free -n stu02 class
  Logical volume "stu02" created.

5.格式化逻辑卷，stu01为xfs，stu02为ext4，设置自动挂载，挂载后就可以使用了。

[root@localhost ~]# mkfs.xfs /dev/class/stu01
meta-data=/dev/class/stu01       isize=512    agcount=4, agsize=1638400 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0, sparse=0
data     =                       bsize=4096   blocks=6553600, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal log           bsize=4096   blocks=3200, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0

[root@localhost ~]# mkfs.ext4 /dev/class/stu02
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
983040 inodes, 3930112 blocks
196505 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2151677952
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

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

[root@localhost ~]# mkdir /mnt/stu0{1,2}
[root@localhost ~]# vim /etc/fstab
//最后面添加下面两行内容
/dev/class/stu01        /mnt/stu01      xfs     defaults        0 0
/dev/class/stu02        /mnt/stu02      ext4    defaults        0 0

[root@localhost ~]# mount -a
[root@localhost ~]# df -hT
Filesystem              Type      Size  Used Avail Use% Mounted on
/dev/mapper/centos-root xfs        17G  927M   17G   6% /
devtmpfs                devtmpfs  901M     0  901M   0% /dev
tmpfs                   tmpfs     912M     0  912M   0% /dev/shm
tmpfs                   tmpfs     912M  8.7M  904M   1% /run
tmpfs                   tmpfs     912M     0  912M   0% /sys/fs/cgroup
/dev/sda1               xfs      1014M  143M  872M  15% /boot
tmpfs                   tmpfs     183M     0  183M   0% /run/user/0
/dev/mapper/class-stu01 xfs        25G   33M   25G   1% /mnt/stu01
/dev/mapper/class-stu02 ext4       15G   41M   14G   1% /mnt/stu02

扩容 LVM 逻辑卷#

1.再添加一块20G的磁盘，重启机器，并对其进行分区，全部空间分为一个主分区，类型改为Linux LVM，ID为8e。

[root@localhost ~]# fdisk -l /dev/sd{b..d} | grep -i "linux lvm"
/dev/sdb1            2048    41943039    20970496   8e  Linux LVM
/dev/sdc1            2048    41943039    20970496   8e  Linux LVM
/dev/sdd1            2048    41943039    20970496   8e  Linux LVM

2.将/dev/sdd1转换为物理卷。

[root@localhost ~]# pvcreate /dev/sdd1
  Physical volume "/dev/sdd1" successfully created.

3.若是卷组剩余空间不够，就要先对class卷组进行扩容。

[root@localhost ~]# vgdisplay class
  --- Volume group ---
  VG Name               class
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  6
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               39.99 GiB
  PE Size               4.00 MiB
  Total PE              10238
  Alloc PE / Size       10238 / 39.99 GiB
  Free  PE / Size       0 / 0
  VG UUID               iB1h9h-2uQa-rD7o-GBVK-pOCA-ek2c-TXieLr

[root@localhost ~]# vgextend class /dev/sdd1
  Volume group "class" successfully extended

[root@localhost ~]# vgdisplay class
  --- Volume group ---
  VG Name               class
  System ID
  Format                lvm2
  Metadata Areas        3
  Metadata Sequence No  7
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                3
  Act PV                3
  VG Size               <59.99 GiB
  PE Size               4.00 MiB
  Total PE              15357
  Alloc PE / Size       10238 / 39.99 GiB
  Free  PE / Size       5119 / <20.00 GiB
  VG UUID               iB1h9h-2uQa-rD7o-GBVK-pOCA-ek2c-TXieLr

4.对stu01和stu02都扩容8G，分别使用xfs_growfs和resize2fs在线调整大小。

[root@localhost ~]# lvextend -L +8G /dev/class/stu01
  Size of logical volume class/stu01 changed from 25.00 GiB (6400 extents) to 33.00 GiB (8448 extents).
  Logical volume class/stu01 successfully resized.

[root@localhost ~]# lvextend -L +8G /dev/class/stu02
  Size of logical volume class/stu02 changed from 14.99 GiB (3838 extents) to 22.99 GiB (5886 extents).
  Logical volume class/stu02 successfully resized.

[root@localhost ~]# xfs_growfs /dev/class/stu01
meta-data=/dev/mapper/class-stu01 isize=512    agcount=4, agsize=1638400 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=6553600, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal               bsize=4096   blocks=3200, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 6553600 to 8650752

[root@localhost ~]# resize2fs /dev/class/stu02
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/class/stu02 is mounted on /mnt/stu02; on-line resizing required
old_desc_blocks = 2, new_desc_blocks = 3
The filesystem on /dev/class/stu02 is now 6027264 blocks long.

[root@localhost ~]# df -hT
Filesystem              Type      Size  Used Avail Use% Mounted on
/dev/mapper/centos-root xfs        17G  927M   17G   6% /
devtmpfs                devtmpfs  901M     0  901M   0% /dev
tmpfs                   tmpfs     912M     0  912M   0% /dev/shm
tmpfs                   tmpfs     912M  8.7M  903M   1% /run
tmpfs                   tmpfs     912M     0  912M   0% /sys/fs/cgroup
/dev/sda1               xfs      1014M  143M  872M  15% /boot
/dev/mapper/class-stu01 xfs        33G   33M   33G   1% /mnt/stu01
/dev/mapper/class-stu02 ext4       23G   44M   22G   1% /mnt/stu02
tmpfs                   tmpfs     183M     0  183M   0% /run/user/0

收缩 LVM 逻辑卷#

关于收缩 LVM 逻辑卷，可以参考上面的命令lvreduce。这会涉及到数据安全性问题，谨慎使用。

总结#

内容不多，但是还要实际操作才能了解。就是三步走，创建物理卷，创建卷组，创建逻辑卷，然后格式化并挂载使用。扩容的话，没有挂载使用，就正常扩，然后格式化挂载，已经挂载使用了，扩容后在线调整生效。还有下一篇关于磁盘配额。