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Linux LVM硬盘管理及LVM扩容 -包含VG扩容、LV扩容、LV缩减、LVM快照

LVM: Logical Volume Manager

lvm即为Logical Volume Manager的缩写,意为逻辑卷管理,用于扩展指定分区磁盘大小。

以下是一些必要概念:

  • 物理存储介质(The physical media)
    这里指系统的存储设备:硬盘,如:/dev/hda1、/dev/sda等等,是存储系统最低层的存储单元。
  • 物理卷(physical volume)
    物理卷就是指硬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)
    LVM卷组类似于非LVM系统中的物理硬盘,其由物理卷组成。可以在卷组上创建一个或多个“LVM分区”(逻辑卷),LVM卷组由一个或多个物理卷组成。
  • 逻辑卷(logical volume)
    LVM的逻辑卷类似于非LVM系统中的硬盘分区,在逻辑卷之上可以建立文件系统(比如/home或者/usr等)。
  • PE(physical extent)
    每一个物理卷被划分为称为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。
  • LE(logical extent)
    逻辑卷也被划分为被称为LE(Logical Extents) 的可被寻址的基本单位。在同一个卷组中,LE的大小和PE是相同的,并且一一对应。

这里放一张比较容易理解的逻辑图:

lvm

本文涉及的命令:

pvcreatepvspvdisplaypvscanpvremovepvmovevgcreatevgextendvgreducevgremovevgsvgdisplaylvextendlvreducelvdisplaylvslvremoveresize2fs

示例:

  • 创建10G:卷组(所有分区加起来为10G就行)

  • 使用fdisk创建大小为4G、6G的两个lvm分区(分区类型为8e)

0.安装lvm

  • 从linux内核2.6.9开始,device-mapper模块就已经包含在内,所以只需加载 模块即可:
[root@server ~]# modprobe dm_mod
[root@server ~]# lsmod | grep dm_mod
dm_mod                102467  2 dm_mirror,dm_log
[root@server ~]#  ##出现如上输出则表示加载成功
  • 如果内核达标但依旧没有该模块,Centos可使用yum install device-mapper安装,Debian系列使用apt install device-mapper安装,再运行上述两条命令加载内核模块即可.

1.使用pvcreate创建卷组:

[root@server ~]# pvcreate /dev/sdb{1,2}
 Physical volume "dev/sdb1" successfully created
 Physical volume "/dev/sdb2" successfully created
[root@system ~]# pvs                ##显示当前lvm物理卷
  PV         VG        Fmt  Attr PSize  PFree
  /dev/sda2  vg_system lvm2 a--  19.51g    0
  /dev/sdb1            lvm2 a--   4.01g 4.01g
  /dev/sdb2            lvm2 a--   6.01g 6.01g
[root@system ~]# pvdisplay          #显示所有lvm卷更详细的输出
[root@system ~]# pvdisplay /dev/sdb2   #显示sdb2详细输出
  "/dev/sdb2" is a new physical volume of "6.01 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdb2
  VG Name               
  PV Size               6.01 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               C4gUJr-17Iy-hs9X-YbXi-3jy8-x5LP-T3zDFM

[root@system ~]#

2.使用卷组管理命令

[root@system ~]# vgs                   ##显示当前卷组
  VG        #PV #LV #SN Attr   VSize  VFree
  vg_system   1   2   0 wz--n- 19.51g    0
[root@system ~]# vgcreate myvg /dev/sdb{1,2}           ##创建名为myvg的卷组
  Volume group "myvg" successfully created
[root@system ~]# vgs
  VG        #PV #LV #SN Attr   VSize  VFree                   ##PV表示该卷组内的物理卷个数,LV表示逻辑卷的个数,VSIZE则表示该卷组大小
  myvg        2   0   0 wz--n- 10.01g 10.01g
  vg_system   1   2   0 wz--n- 19.51g     0 
[root@system ~]# vgdisplay myvg                     ##显示myvg的信息
  --- 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               10.01 GiB
  PE Size               4.00 MiB             ##此时PE(盘区)大小默认4M,在创建vg的时候可使用vgcreate -s参数指定PE的大小
  Total PE              2562
  Alloc PE / Size       0 / 0   
  Free  PE / Size       2562 / 10.01 GiB
  VG UUID               BHo0L2-oDSC-DjSb-cYU7-xxfU-3O1o-jxpEY4

[root@system ~]#
  • 删除现有vg(因为此vg上没有数据,为了方便演示则remove,如果有则谨慎删除)重新vgcreate并且使用-s参数指定PE大小:
[root@system ~]# vgremove myvg
  Volume group "myvg" successfully removed
[root@system ~]# vgs
  VG        #PV #LV #SN Attr   VSize  VFree
  vg_system   1   2   0 wz--n- 19.51g    0
[root@system ~]# vgcreate -s 8MB myvg /dev/sdb{1,2}    ##指定PE大小为8G
  Volume group "myvg" successfully created
[root@system ~]# vgdisplay myvg
  --- 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               10.00 GiB
  PE Size               8.00 MiB
  Total PE              1280
  Alloc PE / Size       0 / 0   
  Free  PE / Size       1280 / 10.00 GiB
  VG UUID               LUtTK3-ZuxN-s22z-svqI-2FkG-XXvc-G2SkJa

[root@system ~]# pvdisplay /dev/sdb1
  --- Physical volume ---
  PV Name               /dev/sdb1
  VG Name               myvg
  PV Size               4.01 GiB / not usable 6.51 MiB
  Allocatable           yes
  PE Size               8.00 MiB
  Total PE              512
  Free PE               512
  Allocated PE          0
  PV UUID               bbcRHk-htgR-uVUE-R9Th-cSgs-9v6N-FUvjc6

[root@system ~]#

3.增加物理卷,扩容

假设空间不够用,可以添加物理卷
使用fdisk增加一个lvm类型(8e)的分区(不在同一磁盘也没问题)
此时,我增加了一个/dev/sdb3大小为8G的lvm分区

接着,创建物理卷并扩容到卷组:

[root@system ~]# pvcreate /dev/sdb3
  dev_is_mpath: failed to get device for 8:19
  Physical volume "/dev/sdb3" successfully created
[root@system ~]# vgextend myvg /dev/sdb3
  Volume group "myvg" successfully extended
[root@system ~]# vgdisplay myvg
  --- Volume group ---
  VG Name               myvg
  System ID             
  Format                lvm2
  Metadata Areas        3
  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                3
  Act PV                3
  VG Size               18.00 GiB                ##已经扩容到18G
  PE Size               8.00 MiB
  Total PE              2304
  Alloc PE / Size       0 / 0   
  Free  PE / Size       2304 / 18.00 GiB
  VG UUID               LUtTK3-ZuxN-s22z-svqI-2FkG-XXvc-G2SkJa

[root@system ~]#

4.移除物理卷,缩容

比如这里,把大小为4G的/dev/sdb1移除掉

[root@system ~]# pvmove /dev/sdb1         ##把sdb1的数据移到其他数据卷上去
  No data to move for myvg                ##显示sdb1没有数据,如果有的话则会等待一段时间
[root@system ~]# vgreduce myvg /dev/sdb1
  Removed "/dev/sdb1" from volume group "myvg"
[root@system ~]# vgdisplay myvg
  --- Volume group ---
  VG Name               myvg
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  3
  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               14.00 GiB
  PE Size               8.00 MiB
  Total PE              1792
  Alloc PE / Size       0 / 0   
  Free  PE / Size       1792 / 14.00 GiB
  VG UUID               LUtTK3-ZuxN-s22z-svqI-2FkG-XXvc-G2SkJa

[root@system ~]# pvremove /dev/sdb1            ##把sdb1物理卷移除,现在sdb1不是pv了
  Labels on physical volume "/dev/sdb1" successfully wiped
[root@system ~]# pvs
  PV         VG        Fmt  Attr PSize  PFree
  /dev/sda2  vg_system lvm2 a--  19.51g    0
  /dev/sdb2  myvg      lvm2 a--   6.00g 6.00g
  /dev/sdb3  myvg      lvm2 a--   8.00g 8.00g
[root@system ~]# vgs
  VG        #PV #LV #SN Attr   VSize  VFree
  myvg        2   0   0 wz--n- 14.00g 14.00g
  vg_system   1   2   0 wz--n- 19.51g     0
[root@system ~]#

5.增加及使用逻辑分区

  • 在myvg创建一个大小为3G,名字为testlv1的逻辑卷:
[root@system ~]# lvcreate -L 3G -n testlv1 myvg
  Logical volume "testlv1" created
[root@system ~]# lvs
  LV      VG        Attr       LSize  Pool Origin Data%  Move Log Cpy%Sync Convert
  testlv1 myvg      -wi-a-----  3.00g                                             
  lv_root vg_system -wi-ao---- 17.51g                                             
  lv_swap vg_system -wi-ao----  2.00g                                             
[root@system ~]#  ls -l /dev/myvg/testlv1
lrwxrwxrwx 1 root root 7 May  5 13:38 /dev/myvg/testlv1 -> ../dm-2
[root@system ~]# ls -l /dev/mapper/myvg-testlv1
lrwxrwxrwx 1 root root 7 May  5 13:38 /dev/mapper/myvg-testlv1 -> ../dm-2             ##划黄色的这两个设备其实都是指向/dev/dm-2这个设备,因此lv是dm设备
[root@system ~]# lvdisplay /dev/myvg/testlv1               ##lvgdisplay显示testlv1逻辑卷具体信息
  --- Logical volume ---
  LV Path                /dev/myvg/testlv1
  LV Name                testlv1
  VG Name                myvg
  LV UUID                qb6pDw-vmDm-9yio-tPLj-wwSa-fEi5-khSuSX
  LV Write Access        read/write
  LV Creation host, time system, 2019-05-05 13:38:48 +0800
  LV Status              available
  # open                 0
  LV Size                3.00 GiB
  Current LE             384
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:2
[root@system ~]#
  • 使用逻辑卷:
[root@system ~]# mke2fs -t ext4 -b 2048 /dev/myvg/testlv1                       #格式化逻辑卷,-b指定block大小
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
Stride=0 blocks, Stripe width=0 blocks
196608 inodes, 1572864 blocks
78643 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=538968064
96 block groups
16384 blocks per group, 16384 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
    16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816, 1327104

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

This filesystem will be automatically checked every 32 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@system ~]# mount /dev/myvg/testlv1 /mnt
[root@system ~]# ls /mnt
lost+found
[root@system ~]#

6.扩容逻辑分区

  • 比如把刚刚的3G扩容到5G大小,使用lvextend
[root@system ~]# vgs                                ##首先使用vgs查看当前卷组中是否有足够的空闲空间去扩容
  VG        #PV #LV #SN Attr   VSize  VFree
  myvg        2   1   0 wz--n- 14.00g 11.00g
  vg_system   1   2   0 wz--n- 19.51g     0
[root@system ~]# lvextend -L 5G /dev/myvg/testlv1                     ##使用-L 5G表示扩容到5G,使用-L +2G则在原来的空间上扩容两G,在这里效果一样
  Extending logical volume testlv1 to 5.00 GiB
  Logical volume testlv1 successfully resized
[root@system ~]# lvs            ##查看当前逻辑卷
  LV      VG        Attr       LSize  Pool Origin Data%  Move Log Cpy%Sync Convert
  testlv1 myvg      -wi-ao----  5.00g                                             
  lv_root vg_system -wi-ao---- 17.51g                                             
  lv_swap vg_system -wi-ao----  2.00g                                             
[root@system ~]# df -h
Filesystem                     Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root   18G  2.5G   14G  16% /
tmpfs                          491M     0  491M   0% /dev/shm
/dev/sda1                      485M   33M  427M   8% /boot
/dev/mapper/myvg-testlv1       3.0G   75M  2.8G   3% /mnt                ##发现扩容之后,/mnt大小并没有发生改变,因为只扩容了物理边界,逻辑边界还没有扩展
[root@system ~]#
  • 扩展逻辑边界:
[root@system ~]# resize2fs /dev/myvg/testlv1               ##后面不接大小默认把/dev/myvg/testlv1逻辑边界扩展到和物理边界一样大
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/myvg/testlv1 is mounted on /mnt; on-line resizing required
old desc_blocks = 2, new_desc_blocks = 3
Performing an on-line resize of /dev/myvg/testlv1 to 2621440 (2k) blocks.
The filesystem on /dev/myvg/testlv1 is now 2621440 blocks long.

[root@system ~]# df -h
Filesystem                     Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root   18G  2.5G   14G  16% /
tmpfs                          491M     0  491M   0% /dev/shm
/dev/sda1                      485M   33M  427M   8% /boot
/dev/mapper/myvg-testlv1       5.0G   75M  4.6G   2% /mnt
[root@system ~]#

7.缩减逻辑分区

  • 例如,把testlv1缩减到2G:
[root@system ~]# umount /dev/myvg/testlv1
[root@system ~]# e2fsck -f /dev/myvg/testlv1                    #检查磁盘
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/testlv1: 11/327680 files (0.0% non-contiguous), 79723/2621440 blocks
[root@system ~]# resize2fs /dev/myvg/testlv1 2G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on /dev/myvg/testlv1 to 1048576 (2k) blocks.
The filesystem on /dev/myvg/testlv1 is now 1048576 blocks long.

[root@system ~]# lvreduce -L 2G /dev/myvg/testlv1
  WARNING: Reducing active logical volume to 2.00 GiB
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce testlv1? [y/n]: y
  Reducing logical volume testlv1 to 2.00 GiB
  Logical volume testlv1 successfully resized
[root@system ~]# mount /dev/myvg/testlv1 /mnt
[root@system ~]# df -h
Filesystem                     Size  Used Avail Use% Mounted on
/dev/mapper/vg_system-lv_root   18G  2.5G   14G  16% /
tmpfs                          491M     0  491M   0% /dev/shm
/dev/sda1                      485M   33M  427M   8% /boot
/dev/mapper/myvg-testlv1       2.0G   74M  1.8G   4% /mnt
[root@system ~]# lvs    ##显示当前逻辑卷
  LV      VG        Attr       LSize  Pool Origin Data%  Move Log Cpy%Sync Convert
  testlv1 myvg      -wi-ao----  2.00g                                             
  lv_root vg_system -wi-ao---- 17.51g                                             
  lv_swap vg_system -wi-ao----  2.00g                                             
[root@system ~]#

8.创建快照卷,并且通过快照卷备份

首先确保卷组内有足够空间可用(vgs)

[root@system ~]# mount            ##查看当前系统挂载状态
/dev/mapper/vg_system-lv_root on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw)
/dev/sda1 on /boot type ext4 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
/dev/mapper/myvg-testlv1 on /mnt type ext4 (rw)
[root@system ~]# lvcreate -s -L 50M -n testv1-snap -p r /dev/myvg/testlv1           -p r表示只读
  Rounding up size to full physical extent 56.00 MiB
  Logical volume "testv1-snap" created
[root@system ~]# mount /dev/myvg/testv1-snap /media/
mount: block device /dev/mapper/myvg-testv1--snap is write-protected, mounting read-only
[root@system ~]# ls /media/        #此时如果修改原卷/mnt下的fstab,快照卷/media下的fstab是不会变的
lost+found     fstab
[root@system ~]# tar -Jcf /tmp/media.tar.xz /dedia/*   ##备份快照卷下的文件
[root@system ~]# umount /media/        ##卸载快照卷
[root@system ~]# lvremove /dev/myvg/testv1-snap        ##移除快照卷
Do you really want to remove active logical volume testv1-snap? [y/n]: y
  Logical volume "testv1-snap" successfully removed
[root@system ~]#

总结:

逻辑卷扩展的步骤:

  • 1、先确定扩展的大小:并确保所属的卷组有足够的剩余空间(vgdisplay);
  • 2、扩展物理边界;
    lvextend -L [+]Size /path/to/lv_device
  • 3、扩展逻辑边界;
    resize2fs /path/to/lv_device

缩减逻辑卷的步骤:

  • 1、卸载卷,并执行强制检测
    e2fsck -f /path/to/lv_device
  • 2、缩减逻辑边界:
    resize2fs /path/to/lv_device SIZE
  • 3、缩减物理边界:
    lvreduce -L [-]Size /path/to/lv_device
  • 快照卷:逻辑卷的一种,通常为只读:
    lvreate -s -L Size -n Name -p r /path/to/original_lv_device
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