LVM
LVM是一种源自Unix环境，在Linux上广泛应用的逻辑虚拟盘存储方案。借助LVM，可以在保证各个Linux目录分区稳定，又可以实现各目录存储资源灵活分配。
本文主要系统介绍Linux环境下，LVM实现资源扩容步骤方法。留待需要朋友待查。
1、环境介绍
笔者使用Linux 6.5进行测试，背景是一台用于测试搭建的数据库服务器，需要转换为正式投产，但是原有可用根节点空间只有50G左右。
[root@Testserver vg_li6]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_li6-lv_root 50G 20G 27G 43% /
tmpfs 3.9G 232K 3.9G 1% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/vg_li6-lv_home 26G 173M 24G 1% /home
目标是通过外围虚拟化环境，增加存储空间，并且将增加的空间转移到/目录下。也就是增加在vg_li6虚拟磁盘组的lv_root逻辑卷下面。
2、增加磁盘空间和分区
联系负责虚拟化的同事，为虚拟机增加虚拟磁盘sdb。通过fdisk命令，可以比较清晰的查看到。
[root@Testserver ~]# fdisk -l
Disk /dev/sda: 85.9 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
（篇幅原因，有省略……）
Disk /dev/sdb: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
使用fdisk命令进行格式化。
[root@Testserver ~]# 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 0x44e9daf0.
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): n –创建新的磁盘组
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-13054, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-13054, default 13054):
Using default value 13054
Command (m for help): w –写入磁盘分区信息
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
查看fdisk结果。
[root@Testserver ~]# fdisk -l
Disk /dev/sda: 85.9 GB, 85899345920 bytes
255 heads, 63 sectors/track, 10443 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00064fe0
Device Boot Start End Blocks Id System
/dev/sda1 * 1 64 512000 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 64 10444 83373056 8e Linux LVM
（篇幅原因，有省略……）
Disk /dev/sdb: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x44e9daf0
Device Boot Start End Blocks Id System
/dev/sdb1 1 13054 104856223+ 83 Linux
3、LVM管理设置
总的步骤应该是这样：首先需要让LVM认可/dev/sdb1是一个可用的PV（Physical Volume），之后将其加入到VG里面去，补充VG资源。最后拓展lv_root磁盘空间。
当前LVM情况如下：
lvm> vgs
VG #PV #LV #SN Attr VSize VFree
vg_li6 1 3 0 wz--n- 79.51g 0
lvm> lvs
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv_home vg_li6 -wi-ao---- 25.63g
lv_root vg_li6 -wi-ao---- 50.00g
lv_swap vg_li6 -wi-ao---- 3.88g
lvm> pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_li6 lvm2 a-- 79.51g 0
此时的pv只有一个/dev/sda2，全部用满。首先创建/dev/sdb1作为PV。
[root@Testserver ~]# pvcreate /dev/sdb1
dev_is_mpath: failed to get device for 8:17
Physical volume "/dev/sdb1" successfully created
[root@Testserver ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_li6 lvm2 a-- 79.51g 0
/dev/sdb1 lvm2 a-- 100.00g 100.00g
往VG里面增加PV，作为空间拓容。
lvm> vgs
VG #PV #LV #SN Attr VSize VFree
vg_li6 1 3 0 wz--n- 79.51g 0
lvm> vgextend vg_li6 /dev/sdb1
Volume group "vg_li6" successfully extended
lvm> vgs
VG #PV #LV #SN Attr VSize VFree
vg_li6 2 3 0 wz--n- 179.50g 100.00g –剩余空间增加
lvm> pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_li6 lvm2 a-- 79.51g 0
/dev/sdb1 vg_li6 lvm2 a-- 100.00g 100.00g
拓展lv_root空间。
[root@Testserver vg_li6]# lvextend -L +70G /dev/vg_li6/lv_root
Extending logical volume lv_root to 120.00 GiB
Logical volume lv_root successfully resized
4、文件系统识别
注意：此时文件系统并没有认可本次增加。
[root@Testserver vg_li6]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_li6-lv_root 50G 20G 27G 43% /
tmpfs 3.9G 232K 3.9G 1% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/vg_li6-lv_home 26G 173M 24G 1% /home
需要使用resize2fs命令进行刷新。
[root@Testserver vg_li6]# resize2fs /dev/vg_li6/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg_li6/lv_root is mounted on /; on-line resizing required
old desc_blocks = 4, new_desc_blocks = 8
Performing an on-line resize of /dev/vg_li6/lv_root to 31457280 (4k) blocks.
The filesystem on /dev/vg_li6/lv_root is now 31457280 blocks long.
[root@Testserver vg_li6]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_li6-lv_root 119G 20G 93G 18% /
tmpfs 3.9G 232K 3.9G 1% /dev/shm
/dev/sda1 485M 39M 421M 9% /boot
/dev/mapper/vg_li6-lv_home 26G 173M 24G 1% /home