Linux逻辑卷管理（LVM）

时间 2020-06-18

标签 linux 逻辑管理 lvm 栏目 Linux 繁體版

原文原文链接

Linux逻辑卷管理（LVM）

LVM基本概念

PV (物理卷)：

能够由硬盘或分区建立。（使用硬盘分区建立时PV时，若原分区已有文件系统，需将分区的id更改成8e,使用fdisk 命令中t选项修改）

VG（卷组）：

由若干个PV组成，建立时候，需指定最小单元PE（物理扩展盘区）大小，并同时将指定的PV加入VG内做为成员。

PE(Physical Extent)：
物理区域是物理卷中可用于分配的最小存储单元，物理区域大小在创建卷组时指定(如不指定默认大小是4MB)，一旦肯定不能更改，同一卷组全部物理卷的物理区域大小需一致，新的pv加入到vg后，pe的大小自动更改成vg中定义的pe大小。LVM技术就是经过在VG中交换PE来实现LV的空间容量扩容或缩减的。

LV（逻辑卷）：

在VG中划分，由若干个PE组成的分区，能够动态调整大小，其空间需小于或等于VG的最大空间。

LVM相关原理示意图以下：node

LVM的操做管理

LVM操做相关命令

pv管理工具centos

显示pv信息

pvs：简要pv信息显示
pvdisplay：显示pv详细信息

建立pv
pvcreate /dev/DEVICE

删除pv
pvremove /dev/DEVICE

vg管理工具app

显示卷组
vgs
vgdisplay

建立卷组
vgcreate [-s #[kKmMgGtTpPeE]] VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]

管理卷组
vgextend VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]
vgreduce VolumeGroupName PhysicalDevicePath [PhysicalDevicePath...]

删除卷组
先作pvmove，再作vgremove

lv管理工具dom

显示逻辑卷
lvs
Lvdisplay

建立逻辑卷
lvcreate -L #[mMgGtT] -n NAME VolumeGroup
lvcreate -l 60%VG -n mylv testvg
lvcreate -l 100%FREE -n yourlv testvg

删除逻辑卷
lvremove /dev/VG_NAME/LV_NAME

重设文件系统大小
fsadm [options] resize device [new_size[BKMGTEP]]
resize2fs [-f] [-F] [-M] [-P] [-p] device [new_size]
xfs_growfs /mountpoint

扩展和缩减逻辑卷ide

扩展逻辑卷：
lvextend -L [+]#[mMgGtT] /dev/VG_NAME/LV_NAME
resize2fs /dev/VG_NAME/LV_NAME
lvresize -r -l +100%FREE /dev/VG_NAME/LV_NAME

缩减逻辑卷：
umount /dev/VG_NAME/LV_NAME
e2fsck -f /dev/VG_NAME/LV_NAME
resize2fs /dev/VG_NAME/LV_NAME #[mMgGtT]
lvreduce -L [-]#[mMgGtT] /dev/VG_NAME/LV_NAME
mount

建立逻辑卷示例工具

建立物理卷
pvcreate /dev/sda3

为卷组分配物理卷
vgcreate vg0 /dev/sda3

从卷组建立逻辑卷
lvcreate -L 256M -n data vg0
mkfs.xfs /dev/vg0/data

挂载
mount /dev/vg0/data /mnt/data

跨主机迁移卷组url

源计算机上
1 在旧系统中，umount全部卷组上的逻辑卷
2 禁用卷组
vgchange –a n vg0
lvdisplay
3 导出卷组
vgexport vg0
pvscan
vgdisplay
拆下旧硬盘

在目标计算机上
4 在新系统中安装旧硬盘，并导入卷组：vgimport vg0
5 vgchange –ay vg0 启用
6 mount全部卷组上的逻辑卷

逻辑卷管理器快照centos7

使用LVM快照
为现有逻辑卷建立快照
lvcreate -l 64 -s -n data-snapshot -p r /dev/vg0/data

挂载快照
mkdir -p /mnt/snap
mount -o ro /dev/vg0/data-snapshot /mnt/snap

恢复快照
umount /dev/vg0/data-snapshot
umount /dev/vg0/data
lvconvert --merge /dev/vg0/data-snapshot

删除快照
umount /mnt/databackup
lvremove /dev/vg0/databackup

实验：扩展逻辑卷

需求：原机器自带一块50G硬盘（设备名/dev/sda），使用LVM分区，先需将 / 分区扩展到100G。步骤以下：spa

一、新增长一块100G硬盘/dev/sdbcode

[root@localhost ~]#fdisk -l

Disk /dev/sda: 53.7 GB, 53687091200 bytes, 104857600 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000b00a8

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200   104857599    51379200   8e  Linux LVM

Disk /dev/mapper/centos-root: 50.5 GB, 50457477120 bytes, 98549760 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes


Disk /dev/sdb: 107.4 GB, 107374182400 bytes, 209715200 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes

二、对新增长硬盘建立pv

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

三、扩展原卷组

查看卷组信息

[root@localhost ~]#vgdisplay 
  --- 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               <49.00 GiB
  PE Size               4.00 MiB
  Total PE              12543
  Alloc PE / Size       12542 / 48.99 GiB
  Free  PE / Size       1 / 4.00 MiB
  VG UUID               I2rPlQ-7z6F-cbV4-vZZk-AK5v-u0FR-NmvCe2

扩展原卷组

[root@localhost ~]#vgextend centos /dev/sdb
  Volume group "centos" successfully extended

查看扩展后卷组信息

[root@localhost ~]#vgdisplay 
  --- Volume group ---
  VG Name               centos
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  4
  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               148.99 GiB
  PE Size               4.00 MiB
  Total PE              38142
  Alloc PE / Size       12542 / 48.99 GiB
  Free  PE / Size       25600 / 100.00 GiB
  VG UUID               I2rPlQ-7z6F-cbV4-vZZk-AK5v-u0FR-NmvCe2

四、扩展 / 分区所在的LV

查看当前：LV状态

[root@localhost ~]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/centos/swap
  LV Name                swap
  VG Name                centos
  LV UUID                0fF8gI-m0lE-kYtz-ML43-5uaS-ze05-jJXBch
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-17 20:50:23 +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                oM5Bcw-tgJ1-6k06-GCdk-sFx3-cy6E-xU3kJs
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-17 20:50:23 +0800
  LV Status              available
  # open                 1
  LV Size                46.99 GiB
  Current LE             12030
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

由以上信息可知 / 分区所属的LV为/dev/centos/root

扩展/dev/centos/root 的空间到100G

[root@localhost ~]#lvextend -r -L +50G /dev/centos/root 
  Size of logical volume centos/root changed from 46.99 GiB (12030 extents) to 96.99 GiB (24830 extents).
  Logical volume centos/root successfully resized.
meta-data=/dev/mapper/centos-root isize=512    agcount=4, agsize=3079680 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=12318720, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal               bsize=4096   blocks=6015, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 12318720 to 25425920

至此，/ 分区逻辑卷空间扩展完成。

逻辑卷的缩减

<font color=#FF0000 size=3>注意：LVM的缩减，只能针对ext系列的文件系统，若是centos7系统默认使用xfs文件系统，LVM只能扩容，不能缩减。</font>

逻辑卷缩减操做步骤：

一、先备份数据（建议备份，不是必须，缩减lv大小有必定风险）

二、umount取消挂载（须要离线缩减）
umount /dev/VG_NAME/LV_NAME

三、须要对文件系统作检查，不然会因警告提示
fsck -f umount /dev/VG_NAME/LV_NAME

四、缩减文件系统到指定大小
resize2fs /dev/VG_NAME/LV_NAME #[mMgGtT]

五、缩减lv到指定大小
lvreduce -L [-]#[mMgGtT] /dev/VG_NAME/LV_NAME

六、从新挂载lv到对应的挂载点
mount /dev/VG_NAME/LV_NAME /mountpoint

逻辑卷的快照管理

对现有逻辑卷(/dev/centos/root)建立快照

[root@localhost ~]#lvcreate -s -n root_snapshot -L 10G /dev/centos/root
  Logical volume "root_snapshot" created.
[root@localhost ~]#

查看快照结果

[root@localhost ~]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/centos/swap
  LV Name                swap
  VG Name                centos
  LV UUID                0fF8gI-m0lE-kYtz-ML43-5uaS-ze05-jJXBch
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-17 20:50:23 +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/data
  LV Name                root
  VG Name                centos
  LV UUID                oM5Bcw-tgJ1-6k06-GCdk-sFx3-cy6E-xU3kJs
  LV Write Access        read/write
  LV Creation host, time localhost, 2019-08-17 20:50:23 +0800
  LV snapshot status     source of
                         root_snapshot [active]
  LV Status              available
  # open                 1
  LV Size                96.99 GiB
  Current LE             24830
  Segments               2
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/centos/data_snapshot
  LV Name                root_snapshot
  VG Name                centos
  LV UUID                CLDfvM-9paq-ea6H-Hz1C-BYPr-eiGF-7hmqFT
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2019-08-18 12:34:31 +0800
  LV snapshot status     active destination for root
  LV Status              available
  # open                 0
  LV Size                96.99 GiB
  Current LE             24830
  COW-table size         10.00 GiB
  COW-table LE           2560
  Allocated to snapshot  0.01%
  Snapshot chunk size    4.00 KiB
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:4

新生成的 /dev/centos/data_snapshot 便是原来/dev/centos/data的快照备份

利用LVM快照恢复数据

<font color=#FF0000 size=2>注意:经过LVM快照方式恢复数据，必须先将原lv和快照lv先umont取消挂载，离线方式进行。</font>

一、将原lv与快照取消挂载
umount /dev/centos/data_snapshot
umount /dev/centos/data

二、使用快照恢复原lv数据
[root@localhost ~]#lvconvert --merge /dev/centos/data_snapshot 
  Delaying merge since origin is open.
  Merging of snapshot centos/root_snapshot will occur on next activation of centos/data.