简单来说就是：

PV：是物理的磁盘分区

VG：LVM中的物理的磁盘分区，也就是PV，必须加入VG，可以将VG理解为一个仓库或者是几个大的硬盘

LV：也就是从VG中划分的逻辑分区

如下图所示PV、VG、LV三者关系：

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特别注意的是：

resize2fs命令            针对的是ext2、ext3、ext4文件系统

xfs_growfs命令         针对的是xfs文件系统

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一、LVM在线扩容

0.查看/home大小为96G

[root@PT233v184 ~]# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/mapper/cl-root 50G 1.7G 49G 4% /

devtmpfs 3.9G 0 3.9G 0% /dev

tmpfs 3.9G 12K 3.9G 1% /dev/shm

tmpfs 3.9G 8.4M 3.9G 1% /run

tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup

/dev/vda1 1014M 139M 876M 14% /boot

/dev/mapper/cl-home 96G 32G 64G 34% /home

tmpfs 783M 0 783M 0% /run/user/1000

1.假设新增的磁盘为/dev/vdb，对磁盘分区。这一步不分区也可行，后文另有说明。

[root@PT233v184 ~]# fdisk /dev/vdb

Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.

Be careful before using the write command.

Device does not contain a recognized partition table

Building a new DOS disklabel with disk identifier 0x304ff336.

Command (m for help): n

Partition type:

p primary (0 primary, 0 extended, 4 free)

e extended

Select (default p): p

Partition number (1-4, default 1):

First sector (2048-629145599, default 2048):

Using default value 2048

Last sector, +sectors or +size{K,M,G} (2048-629145599, default 629145599):

Using default value 629145599

Partition 1 of type Linux and of size 300 GiB is set

Command (m for help): t

Selected partition 1

Hex code (type L to list all codes): 8e

Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): w

The partition table has been altered!

Calling ioctl() to re-read partition table.

Syncing disks.

2.创建PV

[root@PT233v184 ~]# pvcreate /dev/vdb1

Physical volume "/dev/vdb1" successfully created

3.加入VG，lvdisplay查看已存在的"VG Name"，cl

[root@PT233v184 ~]# vgdisplay

--- Volume group ---

VG Name cl

System ID

Format lvm2

Metadata Areas 1

Metadata Sequence No 4

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 3

Open LV 3

Max PV 0

Cur PV 1

Act PV 1

VG Size 149.00 GiB

PE Size 4.00 MiB

Total PE 38143

Alloc PE / Size 38142 / 148.99 GiB

Free PE / Size 1 / 4.00 MiB

VG UUID dGSxPy-2MJ2-TgiB-n3f8-tRCb-NAco-ZCcoSo

[root@PT233v184 ~]# vgextend cl /dev/vdb1

Volume group "cl" successfully extended

4.扩容LV分区，lvdisplay查看要扩容的"LV Path"，/dev/cl/home

[root@PT233v184 ~]# lvdisplay

--- Logical volume ---

LV Path /dev/cl/swap

LV Name swap

VG Name cl

LV UUID NCfBQB-hUSM-ISL0-GUL0-KNru-2qsC-qqoBuE

LV Write Access read/write

LV Creation host, time localhost.localdomain, 2017-10-13 09:24:40 +0800

LV Status available

# open 2

LV Size 3.88 GiB

Current LE 992

Segments 1

Allocation inherit

Read ahead sectors auto

- currently set to 8192

Block device 253:1

--- Logical volume ---

LV Path /dev/cl/home

LV Name home

VG Name cl

LV UUID KUyFmw-TeAX-EcBd-fOX3-vJ00-ceCQ-tHcL4I

LV Write Access read/write

LV Creation host, time localhost.localdomain, 2017-10-13 09:24:40 +0800

LV Status available

# open 1

LV Size 95.12 GiB

Current LE 24350

Segments 1

Allocation inherit

Read ahead sectors auto

- currently set to 8192

Block device 253:2

--- Logical volume ---

LV Path /dev/cl/root

LV Name root

VG Name cl

LV UUID 7u7ZgM-Zn2l-n2ET-y3Ec-EFHx-bzyP-sNVsJK

LV Write Access read/write

LV Creation host, time localhost.localdomain, 2017-10-13 09:24:41 +0800

LV Status available

# open 1

LV Size 50.00 GiB

Current LE 12800

Segments 1

Allocation inherit

Read ahead sectors auto

- currently set to 8192

Block device 253:0

#vgdisplay查看可用空间"Free PE / Size"，76800

[root@PT233v184 ~]# vgdisplay

--- Volume group ---

VG Name cl

System ID

Format lvm2

Metadata Areas 2

Metadata Sequence No 5

VG Access read/write

VG Status resizable

MAX LV 0

Cur LV 3

Open LV 3

Max PV 0

Cur PV 2

Act PV 2

VG Size 448.99 GiB

PE Size 4.00 MiB

Total PE 114942

Alloc PE / Size 38142 / 148.99 GiB

Free PE / Size 76800 / 300.00 GiB

VG UUID dGSxPy-2MJ2-TgiB-n3f8-tRCb-NAco-ZCcoSo

[root@PT233v184 ~]# lvextend -l +76800 /dev/cl/home

Size of logical volume cl/home changed from 95.12 GiB (24350 extents) to 395.12 GiB (101150 extents).

Logical volume cl/home successfully resized.

4.a.多种lvextend扩容参数

lvextend -L 390G /dev/cl/home #增大至390G

lvextend -L +300G /dev/cl/home #增加300G

lvextend -l 100126 /dev/cl/home #增加至100126个PE

lvextend -l +76800 /dev/cl/home #增加76800个PE

lvextend -l +100%FREE /dev/cl/home #剩余的空间全部增加给LV

5.执行重设大小

ext2/ext3/ext4文件系统的调整命令是resize2fs

resize2fs /dev/cl/home

xfs文件系统的调整命令是xfs_growfs

xfs_growfs /dev/cl/home

[root@PT233v184 ~]# xfs_growfs /dev/cl/home

meta-data=/dev/mapper/cl-home isize=512 agcount=4, agsize=6233600 blks

= sectsz=512 attr=2, projid32bit=1

= crc=1 finobt=0 spinodes=0

data = bsize=4096 blocks=24934400, imaxpct=25

= sunit=0 swidth=0 blks

naming =version 2 bsize=4096 ascii-ci=0 ftype=1

log =internal bsize=4096 blocks=12175, version=2

= sectsz=512 sunit=0 blks, lazy-count=1

realtime =none extsz=4096 blocks=0, rtextents=0

data blocks changed from 24934400 to 103577600

6.再次查看/home大小

[root@PT233v184 ~]# df -h

Filesystem Size Used Avail Use% Mounted on

/dev/mapper/cl-root 50G 1.7G 49G 4% /

devtmpfs 3.9G 0 3.9G 0% /dev

tmpfs 3.9G 12K 3.9G 1% /dev/shm

tmpfs 3.9G 8.4M 3.9G 1% /run

tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup

/dev/vda1 1014M 139M 876M 14% /boot

/dev/mapper/cl-home 396G 34G 362G 9% /home

tmpfs 783M 0 783M 0% /run/user/1000

二、LVM初次增加

#磁盘分区

无论新挂载点或者现有挂载点在线扩容，不需要分区，直接pvcreate走起，我也不知道磁盘分区的目的是什么了，可能是不想把整块磁盘的空间全部扩容给lv吧。

# 创建PV、VG、LV

pvcreate /dev/vdb

vgcreate vg_data /dev/vdb

lvcreate -l 25599 -n lv_data vg_data

lvcreate -l +100%FREE -n lv_data vg_data

# 格式化磁盘

mkfs.xfs /dev/vg_data/lv_data

# 修改/etc/fstab，挂载磁盘

echo "/dev/vg_data/lv_data /data xfs defaults 0 0" >> /etc/fstab

mkdir -p /data

mount -a

df -h

三、LVM减小磁盘