LVM卷管理工具

机制概述

Linux 磁盘分区大小分配一般难以准确评估，而且分区大小确定之后无法更改，当数据占满分区时，就需要使用磁盘分区工具进行数据的备份以便重新规划分区大小，同时也需要重洗引导操作系统，因此这不能满足服务器服务的可持续性特性，会造成业务数据的中断。LVM的出现解决了这个难题，LVM 是Linux 下对磁盘分区进行管理的一种机制。通过在物理设备层和文件系统之间增加抽象层，屏蔽下层物理设备（可以是磁盘、磁盘分区、raid）的布局，提供一个抽象的存储卷，在存储卷上建立操作系统。

架构

卷管理

卷管理命令一览表：

物理卷管理

1. 查看系统装载的磁盘，并使用sdb做测试。

[root@linuxde dev]# 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: 0x0000783f

   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        2611    20458496   8e  Linux LVM

Disk /dev/sdb: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 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


Disk /dev/mapper/VolGroup-lv_root: 18.9 GB, 18865979392 bytes
255 heads, 63 sectors/track, 2293 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


Disk /dev/mapper/VolGroup-lv_swap: 2080 MB, 2080374784 bytes
255 heads, 63 sectors/track, 252 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
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2. 初始化sdb磁盘为PV。

[root@linuxde dev]# pvcreate /dev/sdb 
  Physical volume "/dev/sdb" successfully created
[root@linuxde dev]# pvs
  PV         VG       Fmt  Attr PSize  PFree 
  /dev/sda2  VolGroup lvm2 a--  19.51g     0 
  /dev/sdb            lvm2 ---  10.00g 10.00g
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卷组管理

添加PV 到卷组

[root@linuxde dev]# vgcreate datavg /dev/sdb 
  Volume group "datavg" successfully created
[root@linuxde dev]# vgs
  VG       #PV #LV #SN Attr   VSize  VFree 
  VolGroup   1   2   0 wz--n- 19.51g     0 
  datavg     1   0   0 wz--n- 10.00g 10.00g
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逻辑卷管理

在卷组上建立LV

[root@linuxde dev]# lvcreate -n lv1 -L 200M datavg
  Logical volume "lv1" created
[root@linuxde dev]# lvs
  LV      VG       Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root VolGroup -wi-ao----  17.57g                                                    
  lv_swap VolGroup -wi-ao----   1.94g                                                    
  lv1     datavg   -wi-a----- 200.00m
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挂载文件系统

格式化文件系统并挂载文件系统

[root@linuxde dev]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       18G  4.1G   13G  25% /
tmpfs                 491M     0  491M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
[root@linuxde dev]# mount /dev/datavg/lv1 /mnt
mount: you must specify the filesystem type
[root@linuxde dev]# mkf
mkfifo        mkfontscale   mkfs.cramfs   mkfs.ext3     mkfs.ext4dev  mkfs.vfat     
mkfontdir     mkfs          mkfs.ext2     mkfs.ext4     mkfs.msdos    
[root@linuxde dev]# mkfs.ext4 /dev/datavg/lv1 
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
51200 inodes, 204800 blocks
10240 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67371008
25 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks: 
        8193, 24577, 40961, 57345, 73729

Writing inode tables: done                            
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 31 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@linuxde dev]# mount /dev/datavg/lv1 /mnt
[root@linuxde dev]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       18G  4.1G   13G  25% /
tmpfs                 491M     0  491M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/mapper/datavg-lv1
                      190M  1.6M  179M   1% /mnt
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到此为止，我们就可以操作该文件系统了。

扩展逻辑卷

扩展完LV 后还需要使用resize2fs扩容ext4文件系统。xfs文件系统需要使用xfs_growfs命令，使用方式“xfs_growfs {monit_ponit}”

[root@linuxde dev]# lvextend -L +100M /dev/datavg/lv1 
  Size of logical volume datavg/lv1 changed from 200.00 MiB (50 extents) to 300.00 MiB (75 extents).
  Logical volume lv1 successfully resized
[root@linuxde dev]# lvs
  LV      VG       Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root VolGroup -wi-ao----  17.57g                                                    
  lv_swap VolGroup -wi-ao----   1.94g                                                    
  lv1     datavg   -wi-ao---- 300.00m                                                    
[root@linuxde dev]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       18G  4.1G   13G  25% /
tmpfs                 491M     0  491M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/mapper/datavg-lv1
                      190M  1.6M  179M   1% /mnt
[root@linuxde dev]# resize2fs /dev/datavg/lv1 
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/datavg/lv1 is mounted on /mnt; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/datavg/lv1 to 307200 (1k) blocks.
The filesystem on /dev/datavg/lv1 is now 307200 blocks long.

[root@linuxde dev]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       18G  4.1G   13G  25% /
tmpfs                 491M     0  491M   0% /dev/shm
/dev/sda1             477M   28M  424M   7% /boot
/dev/mapper/datavg-lv1
                      287M  2.1M  270M   1% /mnt