存在多个物理硬盘

可以理解为linux下的物理磁盘或者磁盘分区，如/dev/sdb（磁盘）、/dev/sdb1（磁盘分区，通过fdisk对/dev/sdb进行操作划分出来的磁盘分区，类似于windows下的C、D、E盘），但是和物理磁盘以及磁盘分区不同的是，物理卷含有和 LVM相关的参数

以下案例均是/dev/sda 为系统盘，/dev/sdb 为数据盘

1. 创建物理卷

pvcreate /dev/sdb

$ pvcreate /dev/sdb
$ Physical volume "/dev/sdb" successfully created.

2. 查看物理卷

pvdisplay

   [root@localhost ~]# pvdisplay
     --- Physical volume ---
     PV Name               /dev/sda2
     VG Name               centos
     PV Size               9.51 GiB / not usable 3.00 MiB
     Allocatable           yes 
     PE Size               4.00 MiB
     Total PE              2434
     Free PE               10
     Allocated PE          2424
     PV UUID               P6xf6f-NPgl-s3Dm-123h-B5e3-NJBh-GbNM1n
      
     "/dev/sdb" is a new physical volume of "30.00 GiB"
     --- NEW Physical volume ---
     PV Name               /dev/sdb
     VG Name               
     PV Size               30.00 GiB
     Allocatable           NO
     PE Size               0   
     Total PE              0
     Free PE               0
     Allocated PE          0
     PV UUID               eCPH0s-ptje-nqgd-42jW-e2c5-iay3-rRw2hY

3. 查看lv的信息

lvdisplay

[root@localhost ~]# lvdisplay
     --- Logical volume ---
     LV Path                /dev/centos/swap
     LV Name                swap
     VG Name                centos
     LV UUID                9SLqUm-dXfi-bNle-wdX1-cnZQ-HCun-nGWdXk
     LV Write Access        read/write
     LV Creation host, time localhost.localdomain, 2016-06-28 02:34:19 +0800
     LV Status              available
     # open                 2
     LV Size                1.00 GiB
     Current LE             256
     Segments               1
     Allocation             inherit
     Read ahead sectors     auto
     - currently set to     8192
     Block device           253:1
      
     --- Logical volume ---
     LV Path                /dev/centos/root
     LV Name                root
     VG Name                centos
     LV UUID                J3ANyS-BTG5-YJ8M-2Zsq-sBUo-YVWg-jyFmvA
     LV Write Access        read/write
     LV Creation host, time localhost.localdomain, 2016-06-28 02:34:19 +0800
     LV Status              available
     # open                 1
     LV Size                <8.47 GiB
     Current LE             2168
     Segments               1
     Allocation             inherit
     Read ahead sectors     auto
     - currently set to     8192
     Block device           253:0

4. 查看系统中的卷组，，查看VG Name，检查 VG Size/ Free PE / Size原大小

物理块（PE，physical extent）
每个物理卷被分为若干个物理块，是LVM寻址中的最小单元，有唯一编号，可以设置大小，默认为4MB

vgdisplay

   [root@localhost ~]# vgdisplay
     --- Volume group ---
     VG Name               centos
     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               <9.51 GiB
     PE Size               4.00 MiB
     Total PE              2434
     Alloc PE / Size       2424 / <9.47 GiB
     Free  PE / Size       10 / 40.00 MiB
     VG UUID               OyB5dN-0LOk-6vb1-Qmtu-1EQp-1GtB-Szuco0

5. 添加到卷组 centos 中，并查看

vgextend centos /dev/sdb

  [root@localhost ~]# vgextend  centos  /dev/sdb
     Volume group "centos" successfully extended
   [root@localhost ~]# vgs
     VG     #PV #LV #SN Attr   VSize  VFree  
     centos   2   2   0 wz--n- 79.50g <70.04g

6. 为根目录进行扩容（+10G，+100%FREE ）

lvextend -L +10G /dev/centos/root

   [root@localhost ~]# lvextend -L  +10G  /dev/centos/root   
     Size of logical volume centos/root changed from <8.47 GiB (2168 extents) to <18.47 GiB (4728 extents).
     Logical volume centos/root successfully resized.

7. 刷新文件系统

resize2fs /dev/centos/root

   [root@localhost ~]# resize2fs  /dev/centos/root
   resize2fs 1.42.9 (28-Dec-2013)
   resize2fs: Bad magic number in super-block while trying to open /dev/centos/root
   Couldn't find valid filesystem superblock.

如果出现，Bad magic number in super-block 当尝试打开 /dev/centos/root 时 找不到有效的文件系统超级块.

请使用xfs_growfs /dev/centos/root

8. 查看文件系统/挂载点的存储使用情况

df -Th