LVM逻辑卷

Posted 2021-01-27

LVM

逻辑卷（Logical Volume）是由逻辑磁盘形成的虚拟盘，也可称为磁盘分区。
用途：解决分区空间不够用或者分区空间绰绰有余的情况。
逻辑卷的工作原理：逻辑卷（lv）是将几个磁盘分区或者块设备组织起来形成一个大的扩展分区（卷组），该扩展分区不能直接用，需要将其划分成逻辑卷（lv）才能使用，lv可以格式化成不同的文件系统，挂载后直接使用。 lv的扩展和缩减是不会影响原有数据的，但逻辑卷缩减的风险大于逻辑卷扩展的风险。逻辑卷可以支持快照功能。

创建LVM

1.首先创建两个分区/硬盘来,下例为sdb1分区和sdc1分区

[[email protected] ~]#fdisk -l /dev/sdb /dev/sdc 

Disk /dev/sdb: 161.1 GB, 161061273600 bytes, 314572800 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: 0x90c3db64

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048    41945087    20971520   8e  Linux LVM

Disk /dev/sdc: 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
Disk label type: dos
Disk identifier: 0x000c72ff

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1            2048    41945087    20971520   8e  Linux LVM

2.创建PV 使用pvcreate/dev/DEVICE把两个分区创建为PV,用pvs/pvdisplay查看PV信息。

[[email protected] ~]#pvcreate /dev/sdb1 /dev/sdc1
  Physical volume "/dev/sdb1" successfully created.
  Physical volume "/dev/sdc1" successfully created.
[[email protected] ~]#pvdisplay 
  "/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               gIYSbC-QrkI-MRto-xMdP-PJoX-vq40-0JUhSK

  "/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               ONZUYP-4RfT-HDny-c2QD-yi8R-ecsF-n76KkI

3.创建VG vgcreate "vgname" /dev/sd 创建VG,加-s 可以指定PE大小，vgs/vgdisplay查看VG信息

[[email protected] ~]#vgcreate vg1 /dev/sdb1 /dev/sdc1
  Volume group "vg1" successfully created
[[email protected] ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree 
  vg1   2   0   0 wz--n- 39.99g 39.99g

4.创建LV lvcreate常见选项如下

-n 指定LV的名称
-L 指定lv的大小

[[email protected] ~]#lvcreate -n lv_mysql -L 15G vg1
  Logical volume "lv_mysql" created.
[[email protected] ~]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/vg1/lv_mysql
  LV Name                lv_mysql
  VG Name                vg1
  LV UUID                jycUPI-cTfZ-n1Pe-aHA7-g16p-2PMH-PkAA1F
  LV Write Access        read/write
  LV Creation host, time centos7.5.localdomain, 2018-10-23 15:36:57 +0800
  LV Status              available
  # open                 0
  LV Size                15.00 GiB
  Current LE             3840
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

5.设置文件系统，挂载。

[[email protected] ~]#mkfs.ext4 /dev/vg1/lv_mysql
[[email protected] ~]#mount /dev/vg1/lv_mysql /mnt

删除LV VG PV命令

删除逻辑卷
lvremove/dev/VG_NAME/LV_NAME
删除卷组
先做pvmove，再做vgremove
删除pv
pvremove/dev/DEVICE

扩展PVM

1.如果正在使用的某个lv空间快要满的时候，可以给lv增加空前，前提是VG里有空闲的空间。lvextend -l 可以指定pe大小扩展空间，可以用百分百表示，-L直接写单位。

[[email protected] ~]#lvextend -l +50%FREE /dev/vg1/lv_mysql
[[email protected] ~]#lvextend -L +1G /dev/vg1/lv_mysql

2.指定完需要增加空间的大小之后用xfs_growfs更新，etx系列的文件系统用resize2fs

[[email protected] ~]#xfs_growfs /dev/vg1/lv_mysql 
meta-data=/dev/mapper/vg1-lv_mysql isize=512    agcount=4, agsize=983040 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=1        finobt=0 spinodes=0
data     =                       bsize=4096   blocks=3932160, imaxpct=25
         =                       sunit=0      swidth=0 blks
naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
log      =internal               bsize=4096   blocks=2560, version=2
         =                       sectsz=512   sunit=0 blks, lazy-count=1
realtime =none                   extsz=4096   blocks=0, rtextents=0
data blocks changed from 3932160 to 10483712

为卷组扩展空间

1.如果卷组的的空间不够了也可以扩展，先看下卷组空间可用空间已经为0

[[email protected] ~]#vgs
  VG  #PV #LV #SN Attr   VSize  VFree
  vg1   2   1   0 wz--n- 39.99g    0

2.先找一块硬盘，把他设置为PV,pvs显示sde硬盘没有加入到任何卷组。

[[email protected] ~]#pvcreate /dev/sde
WARNING: dos signature detected on /dev/sde at offset 510. Wipe it? [y/n]: y
  Wiping dos signature on /dev/sde.
  Physical volume "/dev/sde" successfully created.
[[email protected] ~]#pvs
  PV         VG  Fmt  Attr PSize   PFree 
  /dev/sdb1  vg1 lvm2 a--  <20.00g     0 
  /dev/sdc1  vg1 lvm2 a--  <20.00g     0 
  /dev/sde       lvm2 ---   50.00g 50.00g

3.把硬盘加入到指定的卷组vgextend

[r[email protected] ~]#vgextend vg1 /dev/sde
  Volume group "vg1" successfully extended
[[email protected] ~]#vgs
  VG  #PV #LV #SN Attr   VSize   VFree  
  vg1   3   1   0 wz--n- <89.99g <50.00g

4.卷组扩展完毕之后就可以再给卷组里其他逻辑卷扩展空间了

lvextend -r -L 100G /dev/vg1/lv_mysql

5.删除卷组里的pv设备 vgreduce

[[email protected] ~]#vgreduce vg1 /dev/sde
  Removed "/dev/sde" from volume group "vg1"

缩减逻辑卷

只有在ext系列上才可以缩减逻辑卷，在xfs的文件系统上不支持此操作。
操作步骤

1，取消挂载
2，先缩减文件系统
3，再缩减逻辑卷大小
(1)卸载逻辑卷
(2)缩减文件系统为20Gresize2fs

[[email protected] ~]#resize2fs /dev/vg1/lv_mysql 20G
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: New size smaller than minimum (64422)

3.缩减逻辑卷lvreduce

[[email protected] ~]#lvreduce -L 20G /dev/vg1/lv_mysql 
  WARNING: Reducing active logical volume to 20.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce vg1/lv_mysql? [y/n]: y
  Size of logical volume vg1/lv_mysql changed from 39.99 GiB (10238 extents) to 20.00 GiB (5120 extents).
  Logical volume vg1/lv_mysql successfully resized.

4.重新挂载逻辑卷

逻辑卷命令

lvextend -r -L ：扩展逻辑卷空间使用
lvremove ：删除逻辑卷
resize2fs ：缩减文件系统大小
lvreduce -L： 缩减逻辑卷大小
vgextend ： 扩展卷组，把新的pv加入到卷组
resize2fs /dev/vg/ ext4
xfs_growfs /dev/vg/ xfs
vgreduce ：删除卷组里的pv设备
vgrename ： 卷组改名
pvmove ：可以把pv上使用的pe迁移到相同卷组的其他pv上
pcscan : 扫描

迁移逻辑卷

[[email protected] ~]#pvmove /dev/sdc1 
  /dev/sdc1: Moved: 100.00%

迁移vg1卷组，查看下卷组下的pv

[[email protected] ~]#pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               vg1
  PV Size               20.00 GiB / not usable 4.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              5119
  Free PE               2559
  Allocated PE          2560
  PV UUID               ONZUYP-4RfT-HDny-c2QD-yi8R-ecsF-n76KkI

1.首先取消挂载
2.把卷组设置为禁用状态vgchange–an 激活为-ay

[[email protected] ~]#vgchange -an vg1
  0 logical volume(s) in volume group "vg1" now active

3.把卷组下的逻辑卷设置为导出状态vgexport vg1 导入为vgimport vg

[[email protected] ~]#vgexport vg1
  Volume group "vg1" successfully exported
[[email protected] ~]#lvdisplay 
  Volume group vg1 is exported

4.设置为导出状态之后，就可以把磁盘拔下来插入到其他服务器上面，然后再把导出状态改为导入，把禁用状态激活即可

LVM快照

快照就是将当时的系统信息记录下来，就好像照相一般，若将来有任何数据改动了，则原始数据会被移动到快照区，没有改动的区域则由快照区和文件系统共享。
建立快照的卷大小只需要原始逻辑卷的15%～20%就够了,也可以使用lvextend放大快照
快照只会保留原有的文件，新建的文件没有

创建一个快照

基于ext系统
也是用lvcreate; -s指明是一个逻辑卷的快照

[[email protected] lv]#lvcreate -n kuaizhao -s -L 2G /dev/vg1/lv_mysql
  Logical volume "kuaizhao" created.
[email protected] lv]#lvdisplay 
  --- Logical volume ---
  LV Path                /dev/vg1/lv_mysql
  LV Name                lv_mysql
  VG Name                vg1
  LV UUID                jycUPI-cTfZ-n1Pe-aHA7-g16p-2PMH-PkAA1F
  LV Write Access        read/write
  LV Creation host, time centos7.5.localdomain, 2018-10-23 15:36:57 +0800
  LV snapshot status     source of
                         kuaizhao [active]
  LV Status              available
  # open                 1
  LV Size                10.00 GiB
  Current LE             2560
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0

  --- Logical volume ---
  LV Path                /dev/vg1/kuaizhao
  LV Name                kuaizhao
  VG Name                vg1
  LV UUID                dk8cT0-Ykl5-p3CW-LGsc-KxIA-3oMl-iESK0J
  LV Write Access        read/write
  LV Creation host, time centos7.5.localdomain, 2018-10-23 17:51:11 +0800
  LV snapshot status     active destination for lv_mysql
  LV Status              available
  # open                 0
  LV Size                10.00 GiB
  Current LE             2560
  COW-table size         2.00 GiB
  COW-table LE           512
  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           253:3

还原快照

还原快照先取消挂载
还原快照用lvconvert--merge +快照路径命令可以把快照还原到原来的逻辑卷

[[email protected] mnt]#lvconvert --merge /dev/vg1/kuaizhao 
  Merging of volume vg1/kuaizhao started.
  vg1/lv_mysql: Merged: 100.00%

基于xfs
xfs系统里创建好快照之后，在挂载的时候要使用mount -o nouuid不检查uuid，因为创建的快照UUID和逻辑卷的UUID是相同的

删除快照

lvremove /dev/vg1/kuaizhao