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简单易懂讲解LVM

article 2025/1/17 17:53:02

1、LVM是什么？

LVM是管理磁盘的一种方式，特点是灵活调整大小，方便空间扩容

2、LVM整个流程

物理硬盘变成–物理卷PV–加入卷组VG–制作逻辑卷LV–格式化–挂载

3、查看现有的物理卷

通过使用pvdisplay命令查看物理卷，这里有两个物理卷，分别是/dev/sda2和/dev/sdc，这里的PE Size是一个存储单元4MiB，Total PE为共计有4994个存储单元，PV的大小为4X4994/1024=19.51GiB

[root@linuxprobe ~]# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               rhel
  PV Size               19.51 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              4994
  Free PE               0
  Allocated PE          4994
  PV UUID               IqpyhR-Gk1a-Hew8-aaY3-xCtQ-Guus-PS4D6L
   
  "/dev/sdc" is a new physical volume of "5.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdc
  VG Name               
  PV Size               5.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               8ixdTd-I0Rn-47b1-Spkm-wqMe-iFnb-7KiIW9

4、查看现有卷组

通过vgdisplay命令查看卷组，这里的卷组名为rhel

[root@linuxprobe ~]# vgdisplay 
  --- Volume group ---
  VG Name               rhel
  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               19.51 GiB
  PE Size               4.00 MiB
  Total PE              4994
  Alloc PE / Size       4994 / 19.51 GiB
  Free  PE / Size       0 / 0   
  VG UUID               oSiZYq-GjEe-AyTH-YfUm-xq94-yIDA-5LG9k3

5、查看逻辑卷

通过使用lvdisplay命令查看逻辑卷，这里有两个逻辑卷，分别为swap和root

[root@linuxprobe ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/rhel/swap
  LV Name                swap
  VG Name                rhel
  LV UUID                FnYPjs-huSu-xmCo-c8p4-WoYV-lsm2-IdVsYC
  LV Write Access        read/write
  LV Creation host, time localhost, 2024-12-07 18:28:11 +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     256
  Block device           253:1
   
  --- Logical volume ---
  LV Path                /dev/rhel/root
  LV Name                root
  VG Name                rhel
  LV UUID                Pzio3Z-wBmP-Q19D-Z9iU-eCZK-5VrK-PiLrIO
  LV Write Access        read/write
  LV Creation host, time localhost, 2024-12-07 18:28:11 +0800
  LV Status              available
  # open                 1
  LV Size                17.51 GiB
  Current LE             4482
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
  [root@linuxprobe ~]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda             8:0    0   20G  0 disk 
├─sda1          8:1    0  500M  0 part /boot
└─sda2          8:2    0 19.5G  0 part 
  ├─rhel-root 253:0    0 17.5G  0 lvm  /
  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]

6、扩展逻辑卷

首先确保物理服务器上有足够的空间或者添加新的硬盘

lsblk查看目前根的大小
lvextend -L +5g /dev/rhel/root
lsblk再次查看空间多了5G，并且是跨越两块磁盘空间，同时vgdisplay查看，rhel卷组可用空间少了5G，但是使用df-h查看还是原来的空间，这里需要注意一下，调整完成逻辑卷大小后，需要对文件系统调整大小进行匹配，使用命令xfs_growfs /dev/rhel/root，如果使用的是ext4则将xfs_growfs换成resize2fs

[root@linuxprobe ~]# pvcreate /dev/sdc
  Physical volume "/dev/sdc" successfully created
  [root@linuxprobe ~]# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               rhel
  PV Size               19.51 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              4994
  Free PE               0
  Allocated PE          4994
  PV UUID               IqpyhR-Gk1a-Hew8-aaY3-xCtQ-Guus-PS4D6L
   
  "/dev/sdc" is a new physical volume of "5.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sdc
  VG Name               
  PV Size               5.00 GiB
  Allocatable           NO
  PE Size               0   
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               8ixdTd-I0Rn-47b1-Spkm-wqMe-iFnb-7KiIW9
[root@linuxprobe ~]# vgextend rhel /dev/sdc
  Volume group "rhel" successfully extended
[root@linuxprobe ~]# vgdisplay 
  --- Volume group ---
  VG Name               rhel
  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               24.50 GiB
  PE Size               4.00 MiB
  Total PE              6273
  Alloc PE / Size       4994 / 19.51 GiB
  Free  PE / Size       1279 / 5.00 GiB
  VG UUID               oSiZYq-GjEe-AyTH-YfUm-xq94-yIDA-5LG9k3
[root@linuxprobe ~]# lsblk
NAME          MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda             8:0    0   20G  0 disk 
├─sda1          8:1    0  500M  0 part /boot
└─sda2          8:2    0 19.5G  0 part 
  ├─rhel-root 253:0    0 17.5G  0 lvm  /
  └─rhel-swap 253:1    0    2G  0 lvm  [SWAP]
sdb             8:16   0   10G  0 disk 
├─sdb1          8:17   0    2G  0 part /newFS
└─sdb2          8:18   0    3G  0 part [SWAP]
sdc             8:32   0    5G  0 disk 
sr0            11:0    1  3.5G  0 rom  /media/cdrom
[root@linuxprobe ~]# lvextend -L +5g /dev/rhel/root
  Extending logical volume root to 22.51 GiB
  Insufficient free space: 1280 extents needed, but only 1279 available
[root@linuxprobe ~]# xfs_growfs /dev/rhel/root