LVM动态扩展

<center> LVM Space Expansion </center>

在平时的开发工作中，经常会创建磁盘不足够大的虚拟机，然后往集群里面写一些数据导致磁盘满了。手动编辑虚拟机的磁盘大小是不会文件系统识别的，大多数同学只能无奈的重新装OS，这里我介绍一种基于LVM实现动态的方式。

LVM了解

LVM是逻辑盘卷管理（LogicalVolumeManager）的简称，它是Linux环境下对磁盘分区进行管理的一种机制，LVM是建立在硬盘和分区之上的一个逻辑层，来提高磁盘分区管理的灵活性。通过LVM系统管理员可以轻松管理磁盘分区，如：将若干个磁盘分区连接为一个整块的卷组（volumegroup），形成一个存储池。管理员可以在卷组上随意创建逻辑卷组（logicalvolumes），并进一步在逻辑卷组上创建文件系统。管理员通过LVM可以方便的调整存储卷组的大小，并且可以对磁盘存储按照组的方式进行命名、管理和分配。

查看分区

当前默认只有一个采用lvm的分区，一开始sda磁盘容量为16G，后来发现不够用了，编辑磁盘大小为50G，但是可以发现这50G并没有起到扩展分区容量的效果。

[root@tony-play ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_tonyplay-lv_root
                       14G  3.4G  9.6G  26% /
tmpfs                 1.9G   72K  1.9G   1% /dev/shm
/dev/sda1             477M   42M  410M  10% /boot

[root@tony-play ~]# 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 15.5G  0 part 
  ├─vg_tonyplay-lv_root (dm-0) 253:0    0 13.9G  0 lvm  /
  └─vg_tonyplay-lv_swap (dm-1) 253:1    0  1.6G  0 lvm  [SWAP]

分区

可以通过新增一块其他磁盘来扩容，我这边采取的是增大当前磁盘的容量实现扩容。

有时候因为系统设备处于繁忙状态，所以分区需要重启后才会生效。

[root@tony-play ~]# fdisk /dev/sda
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): 3
First cylinder (2089-6527, default 2089):   // 直接回车，用默认值就可以了
Using default value 2089
Last cylinder, +cylinders or +size{K,M,G} (2089-6527, default 6527):    // 直接回车，用默认值就可以了
Using default value 6527
Command (m for help): w
The partition table has been altered!

# 可以看到新建的分区sda3已结被创建出来了，采取默认值会将剩余所有空间都分到分区中
[root@tony-play ~]# 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 15.5G  0 part 
│ ├─vg_tonyplay-lv_root (dm-0) 253:0    0 13.9G  0 lvm  /
│ └─vg_tonyplay-lv_swap (dm-1) 253:1    0  1.6G  0 lvm  [SWAP]
└─sda3                           8:3    0   34G  0 part

查看当前文件系统

当前文件系统为ext4

[root@tony-play ~]# mount
/dev/mapper/vg_tonyplay-lv_root on / type ext4 (rw)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
tmpfs on /dev/shm type tmpfs (rw,rootcontext="system_u:object_r:tmpfs_t:s0")
/dev/sda1 on /boot type ext4 (rw)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)

为新分区创建文件系统

[root@tony-play ~]# sudo mkfs.ext4 /dev/sda3
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
2228224 inodes, 8912727 blocks
445636 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
272 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
    4096000, 7962624

Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.

查看卷组信息

[root@tony-play ~]# vgdisplay
  --- Volume group ---
  VG Name               vg_tonyplay     // 卷组名在下面扩展中会用到
  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               15.51 GiB
  PE Size               4.00 MiB
  Total PE              3970
  Alloc PE / Size       3970 / 15.51 GiB
  Free  PE / Size       0 / 0   
  VG UUID               Y9usSM-nDU5-ZAUd-Y3Te-u5Pd-uFBr-gcYHf0

创建新物理卷

[root@tony-play ~]# pvcreate /dev/sda3
  Physical volume "/dev/sda3" successfully created

扩展到卷组

vgextend vg_tonyplay /dev/sda3  // 卷组名在查看卷组信息中
  Volume group "vg_tonyplay" successfully extended

查看逻辑分区

/dev/vg_tonyplay/lv_root就是根分区，也是我们要扩展的分区。

[root@tony-play ~]# lvdisplay 
  --- Logical volume ---
    LV Path                /dev/vg_tonyplay/lv_root   // 根分区
    LV Name                lv_root
    VG Name                vg_tonyplay
    LV UUID                IPd7lm-Sx8g-pe7k-llNL-j1wc-mbA2-2cAdsy
    LV Write Access        read/write
    LV Creation host, time tony-play, 2017-04-10 17:58:53 -0400
    LV Status              available
    # open                 1
    LV Size                13.91 GiB
    Current LE             3561
    Segments               1
    Allocation             inherit
    Read ahead sectors     auto
    - currently set to     256
    Block device           253:0

    --- Logical volume ---
    LV Path                /dev/vg_tonyplay/lv_swap
    LV Name                lv_swap
    VG Name                vg_tonyplay
    LV UUID                qX637q-iD6i-8blp-hmmS-MvLy-xZ0y-b4D0BF
    LV Write Access        read/write
    LV Creation host, time tony-play, 2017-04-10 17:59:07 -0400
    LV Status              available
    # open                 1
    LV Size                1.60 GiB
    Current LE             409
    Segments               1
    Allocation             inherit
    Read ahead sectors     auto
    - currently set to     256
    Block device           253:1

扩展容量到逻辑分区

[root@tony-play ~]# lvextend /dev/vg_tonyplay/lv_root /dev/sda3
  Size of logical volume vg_tonyplay/lv_root changed from 13.91 GiB (3561 extents) to 47.91 GiB (12264 extents).
  Logical volume lv_root successfully resized

刷新逻辑分区容量使扩展生效

ext4用resize2fs，xfs用xfs_growfs

[root@tony-play ~]# resize2fs /dev/vg_tonyplay/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/vg_tonyplay/lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 3
Performing an on-line resize of /dev/vg_tonyplay/lv_root to 12558336 (4k) blocks.
The filesystem on /dev/vg_tonyplay/lv_root is now 12558336 blocks long.

查看逻辑分区容量

可以发现/dev/mapper/vg_tonyplay-lv_root已经从开始的14G扩展到了48G。ok，这就说明大功告成了，再也不用通过重装系统这种蹩脚的方式扩容了

[root@tony-play ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_tonyplay-lv_root
                       48G  3.4G   42G   8% /
tmpfs                 1.9G   72K  1.9G   1% /dev/shm
/dev/sda1             477M   42M  410M  10% /boot

小结

至此，lvm扩容工作的过程应该是比较清楚了，之后有机会的话我会再补充一下LVM的压缩、删除等操作过程。