每当我们生产上线服务器的时候，总是无法正确的预估磁盘大小该给多少，这样就产生了一个技术LVM，什么是LVM？
LVM是 Logical Volume Manager（逻辑卷管理），它是Linux环境下对磁盘分区进行管理的一种机制。
这里菜鸡哥哥画一个图，是我自己的理解，如果有错误请指正！！
那么如何使用lvm呢？
[root@jw ~]# fdisk -l
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 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: 0x00009be7
Device Boot Start End Blocks Id System
/dev/sda1 * 1 26 204800 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 26 287 2097152 82 Linux swap / Solaris
Partition 2 does not end on cylinder boundary.
/dev/sda3 287 2611 18668544 83 Linux
Disk /dev/sdb: 5368 MB, 5368709120 bytes——实验演示使用此盘
255 heads, 63 sectors/track, 652 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: 0xb8acf654
Device Boot Start End Blocks Id System
Disk /dev/sdc: 1073 MB, 1073741824 bytes
255 heads, 63 sectors/track, 130 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
[root@jw ~]# fdisk /dev/sdb——对需要进行lvm的磁盘进行分区
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
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4):
Value out of range.
Partition number (1-4): 1
First cylinder (1-652, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-652, default 652): +1G
Command (m for help): p
Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 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: 0xb8acf654
Device Boot Start End Blocks Id System
/dev/sdb1 1 132 1060258+ 83 Linux
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (133-652, default 133):
Using default value 133
Last cylinder, +cylinders or +size{K,M,G} (133-652, default 652): +1G
Command (m for help): p
Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 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: 0xb8acf654
Device Boot Start End Blocks Id System
/dev/sdb1 1 132 1060258+ 83 Linux
/dev/sdb2 133 264 1060290 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks
[root@jw ~]# pvcreate /dev/sdb{1,2}——创建pv
Physical volume "/dev/sdb1" successfully created
Physical volume "/dev/sdb2" successfully created
[root@jw ~]# vgcreate vg01 /dev/sdb{1,2}——创建vg，vg名为vg01
Volume group "vg01" successfully created
[root@jw ~]# lvcreate -n lv01 -L 1G vg01——创建lv，lv名为lv01，大小为1G
Logical volume "lv01" created
[root@jw ~]#
[root@jw ~]# pvs——查看pv
PV VG Fmt Attr PSize PFree
/dev/sdb1 vg01 lvm2 a-- 1.01g 8.00m
/dev/sdb2 vg01 lvm2 a-- 1.01g 1.01g
[root@jw ~]# vgs——查看vg
VG #PV #LV #SN Attr VSize VFree
vg01 2 1 0 wz--n- 2.02g 1.02g
[root@jw ~]# lvs——查看lv
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv01 vg01 -wi-a----- 1.00g
[root@jw ~]#
[root@jw ~]# pvscan
PV /dev/sdb1 VG vg01 lvm2 [1.01 GiB / 8.00 MiB free]
PV /dev/sdb2 VG vg01 lvm2 [1.01 GiB / 1.01 GiB free]
Total: 2 [2.02 GiB] / in use: 2 [2.02 GiB] / in no VG: 0 [0 ]
[root@jw ~]# vgscan
Reading all physical volumes. This may take a while...
Found volume group "vg01" using metadata type lvm2
[root@jw ~]# lvscan
ACTIVE '/dev/vg01/lv01' [1.00 GiB] inherit
[root@jw ~]#
[root@jw ~]# pvdisplay
--- Physical volume ---
PV Name /dev/sdb1
VG Name vg01
PV Size 1.01 GiB / not usable 3.41 MiB
Allocatable yes
PE Size 4.00 MiB——默认PE大小为4M
Total PE 258
Free PE 2
Allocated PE 256
PV UUID CvlZqo-1Bxi-BKzg-cgGC-W7hZ-43np-SsdyEq
--- Physical volume ---
PV Name /dev/sdb2
VG Name vg01
PV Size 1.01 GiB / not usable 3.44 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 258
Free PE 258
Allocated PE 0
PV UUID pDa7Mj-dCs4-cY0V-4JZY-viUG-BSNI-aspjlN
[root@jw ~]# vgdisplay
--- Volume group ---
VG Name vg01
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 2
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 0
Max PV 0
Cur PV 2
Act PV 2
VG Size 2.02 GiB
PE Size 4.00 MiB
Total PE 516
Alloc PE / Size 256 / 1.00 GiB
Free PE / Size 260 / 1.02 GiB
VG UUID FUhTIi-lmOr-eVOi-JxMA-0pMJ-yMQq-8gSlCa
[root@jw ~]# lvdisplay
--- Logical volume ---
LV Path /dev/vg01/lv01
LV Name lv01
VG Name vg01
LV UUID S4HQMH-jxjp-0WbT-TkiV-Ftc7-dn58-7l3nsy
LV Write Access read/write
LV Creation host, time jw, 2017-12-22 23:06:19 +0800
LV Status available
# open 0
LV Size 1.00 GiB
Current LE 256
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:0
[root@jw ~]# mkfs.ext4 /dev/vg01/lv01 ——格式化lvm，文件系统为ext4
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
65536 inodes, 262144 blocks
13107 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=268435456
8 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 36 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@jw ~]# mkdir /testlvm
[root@jw ~]# mount /dev/vg01/lv01 /testlvm/ 挂载lvm
[root@jw ~]# df -TH
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda3 ext4 19G 4.7G 14G 27% /
tmpfs tmpfs 515M 0 515M 0% /dev/shm
/dev/sda1 ext4 204M 31M 163M 16% /boot
/dev/mapper/vg01-lv01 ext4 **1.1G** 35M 969M 4% /testlvm
[root@jw ~]#
这里演示lv扩容，把/testlvm加大500M
[root@jw ~]# vgs——首先查看vg是否有可用空间
VG #PV #LV #SN Attr VSize VFree——VFree还有1G空闲
vg01 2 1 0 wz--n- 2.02g 1.02g
[root@jw ~]# lvextend -L +500M /dev/vg01/lv01 ——有空间直接扩展
Extending logical volume lv01 to 1.49 GiB
Logical volume lv01 successfully resized
[root@jw ~]#
---------------------------------------------------
如果vgs查看没有空间，则需要添加vg,新格式化一个分区sdc1，这里不演示格式化步骤；
vgextend vg01 /dev/sdc1
Lvextend -L 500M /dev/vg01/lv01
————————————————————
执行以上lv扩容后，执行df -Th 发现还是没有扩容，
linux7对文件系统进行扩容执行以下命令
[root@xuegod61 ~]# xfs_growfs /dev/vg01/lv01
linux6对文件系统进行扩容执行以下命令
[root@xuegod61 ~]# resize2fs /dev/vg01/lv01
这里演示的是格式化ext4，所以使用resize2fs
[root@jw ~]# resize2fs /dev/vg01/lv01
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg01/lv01 is mounted on /testlvm; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/vg01/lv01 to 390144 (4k) blocks.
The filesystem on /dev/vg01/lv01 is now 390144 blocks long.
[root@jw ~]# df -TH
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda3 ext4 19G 4.7G 14G 27% /
tmpfs tmpfs 515M 0 515M 0% /dev/shm
/dev/sda1 ext4 204M 31M 163M 16% /boot
/dev/mapper/vg01-lv01 ext4 **1.6G** 36M 1.5G 3% /testlvm
[root@jw ~]# 删除lvm需要先umount
umount /dev/vg01/lv01
移除lv
lvremove /dev/vg01/lv01
移除vg
vgremove vg01
移除pv
pvremove /dev/sdb{1,2}