生产环境中，经常会遇到硬盘满，这时候需要LVM格式的硬盘扩容。
LVM简介
LVM是逻辑盘卷管理（LogicalVolume Manager）的简称,它是一种磁盘管理工具，最主要的功能就是可以随时在线调整分区的大小，解决了安装Linux系统时需要评估分区大小的烦恼。
LVM相关术语
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，是存储系统最底层的存储单元。
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。
[root@localhost~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_nginx02-lv_root 45G 42G 804M 99% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
[root@localhost~]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sr0 11:0 1 1024M 0 rom
sda 8:0 0 50G 0 disk
├─sda1 8:1 0 500M 0 part /boot
└─sda2 8:2 0 49.5G 0 part
├─vg_nginx02-lv_root (dm-0) 253:0 0 45.6G 0 lvm /
└─vg_nginx02-lv_swap (dm-1) 253:1 0 3.9G 0 lvm [SWAP]
sdb 8:16 0 20G 0 disk
#开始扩容
[root@localhost~]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x492f8aad.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help): p
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
64 heads, 32 sectors/track, 20480 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x492f8aad
Device Boot Start End Blocks Id System
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-20480, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-20480, default 20480):
Using default value 20480
Command (m for help): t
Selected partition 1
Hex code (type L to list codes): L
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx
5 Extended 42 SFS 86 NTFS volume set da Non-FS data
6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility
8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt
9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access
a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs
e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT
f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 61 SpeedStor a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary
16 Hidden FAT16 64 Novell Netware af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 80 Old Minix be Solaris boot ff BBT
1e Hidden W95 FAT1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
# 一定要指定分区的格式为8e，这是LVM的分区格式
[root@localhost ~]# mkfs.ext4 /dev/sdb1
#创建PV
[root@localhost ~]# pvcreate /dev/sdb1
#查看当前已经存在的VG信息
[root@localhost ~]# vgdisplay
#提示
Physical volume "/dev/sdb1" successfully created
[root@localhost ~]# vgdisplay
--- Volume group ---
VG Name vg_nginx02
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 49.51 GiB
PE Size 4.00 MiB
Total PE 12674
Alloc PE / Size 12674 / 49.51 GiB
Free PE / Size 0 / 0
VG UUID WvYqDf-3IW9-FtBO-cs0y-jYZv-Xj2x-ntX9OP
[root@localhost ~]# vgextend vg_nginx02 /dev/sdb1
Volume group "VolGroup"successfully extended
[root@localhost~]# lvextend -L +19.9G /dev/mapper/vg_nginx02-lv_root
Rounding size to boundary between physical extents: 19.90 GiB
Extending logical volume lv_root to 65.54 GiB
Logical volume lv_root successfully resized
[root@localhost~]# resize2fs /dev/mapper/vg_nginx02-lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/mapper/vg_nginx02-lv_root is mounted on /; on-line resizing required
old desc_blocks = 3, new_desc_blocks = 5
Performing an on-line resize of /dev/mapper/vg_nginx02-lv_root to 17179648 (4k) blocks.
The filesystem on /dev/mapper/vg_nginx02-lv_root is now 17179648 blocks long.
若不是xfs我们可以用resize2fs，这里报错了
[root@localhost~]# resize2fs -f /dev/mapper/vg_nginx02-lv_root
resize2fs 1.41.12 (17-May-2010)
resize2fs: Bad magic number in super-block while trying to open /dev/mapper/vg_nginx02-lv_root
Couldn't find valid filesystem superblock.
[root@localhost~]# xfs_growfs /dev/mapper/vg_nginx02-lv_root
[root@localhost~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_nginx02-lv_root 65G 42G 20G 69% /
tmpfs 1.9G 0 1.9G 0% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot