LVM全称是Logical Volume Manager. 它主要是实现硬盘容量的动态扩展. 一般用于存储数据量无法预估的场景, 例如Linux的根目录用lvm存储.
LVM创建过程一般是这样的
1. 硬盘先分区: 一般是一个硬盘一个分区, 或者是多个分区在一个硬盘
命令: fdisk
2. PV(Physcial Volumes)划分, 可以把几个硬盘分区化成PV
命令: pvcreate, pvs, pvdisplay, pvremove, pvmove, pvscan
3. VG(Volume Group), 把几个或所有PV划分成可用空间, 有就是一定大小的块, 块的大小可以自己定义, 默认是4M
命令:vgcreate, vgs, vgdisplay, vgreduce, vgextend, vgscan
4. LV(Logical Volumes), 逻辑卷划分, 将vg划分成大小不超过vg总量的lv
命令: lvcreate, lvs, lvdisplay, lvremove, lvreduce, lvextend, lvscan
5. 格式化磁盘
命令: mke2fs
6. 挂载
命令: mount
实例分别为2G, 3G, 4G的硬盘, 全部划分成pv, 其中的5G划分成lv, 并格式化成ext4.
1. 三块硬盘分别分成3个区
[root@centos ~]# fdisk /dev/sdb
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): p
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 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: 0x289452a0
Device Boot Start End Blocks Id System
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 1
First cylinder (1-6527, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-6527, default 6527): +2G
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2
First cylinder (263-6527, default 263):
Using default value 263
Last cylinder, +cylinders or +size{K,M,G} (263-6527, default 6527): +3G
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 3
First cylinder (656-6527, default 656):
Using default value 656
Last cylinder, +cylinders or +size{K,M,G} (656-6527, default 6527): +4G
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@centos ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 53.7 GB, 53687091200 bytes
255 heads, 63 sectors/track, 6527 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: 0x289452a0
Device Boot Start End Blocks Id System
/dev/sdb1 1 262 2104483+ 83 Linux
/dev/sdb2 263 655 3156772+ 83 Linux
/dev/sdb3 656 1178 4200997+ 83 Linux
2. 三个分区全部转换成pv
[root@centos ~]# pvcreate /dev/sdb{1,2,3}
Physical volume "/dev/sdb1" successfully created
Physical volume "/dev/sdb2" successfully created
Physical volume "/dev/sdb3" successfully created
[root@centos ~]# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2 vg_centos lvm2 a-- 49.51g 0
/dev/sdb1 lvm2 --- 2.01g 2.01g
/dev/sdb2 lvm2 --- 3.01g 3.01g
/dev/sdb3 lvm2 --- 4.01g 4.01g
3. pv转换成vg并且取名testvg
[root@centos ~]# vg testvg /dev/sdb{1,2,3}
-bash: vg: command not found
[root@centos ~]# vgcreate testvg /dev/sdb{1,2,3}
Volume group "testvg" successfully created
[root@centos ~]# vgs
VG #PV #LV #SN Attr VSize VFree
testvg 3 0 0 wz--n- 9.02g 9.02g
vg_centos 1 2 0 wz--n- 49.51g 0
4. 划分成5G lv并且取名testlv
[root@centos ~]# lvcreate testvg -L 5G -n testlv Logical volume "testlv" created [root@centos ~]# lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert testlv testvg -wi-a----- 5.00g lv_root vg_centos -wi-ao---- 47.57g lv_swap vg_centos -wi-ao---- 1.94g
5. 格式化新建的testlv为ext4
[root@centos ~]# mke2fs -t ext4 /dev/testvg/testlv 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 327680 inodes, 1310720 blocks 65536 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=1342177280 40 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 Writing inode tables: done Creating journal (32768 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 28 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override.
6. 加载新建的lv并确定4G
[root@centos ~]# mount /dev/testvg/testlv /data [root@centos ~]# df -lh Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_centos-lv_root 47G 4.7G 40G 11% / tmpfs 495M 72K 495M 1% /dev/shm /dev/sda1 477M 29M 424M 7% /boot /dev/mapper/testvg-testlv 4.8G 10M 4.6G 1% /data
需要几点
1. 扩展物理边界可以直接加硬盘,pvcreate, vgextend, lvextend
[root@centos ~]# lvextend -L 6G testlv Path required for Logical Volume "testlv" Please provide a volume group name Run `lvextend --help‘ for more information. [root@centos ~]# lvextend -L 6G /dev/testvg/testlv Size of logical volume testvg/testlv changed from 5.00 GiB (1280 extents) to 6.00 GiB (1536 extents). Logical volume testlv successfully resized
2.缩减硬盘, 要先离线, 强制检测, 缩减逻辑空间, vgreduce
[root@centos ~]# e2fsck -f /dev/testvg/testlv e2fsck 1.41.12 (17-May-2010) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/testvg/testlv: 12/327680 files (0.0% non-contiguous), 55950/1310720 blocks [root@centos ~]# resize2fs /dev/testvg/testlv 3G resize2fs 1.41.12 (17-May-2010) Resizing the filesystem on /dev/testvg/testlv to 786432 (4k) blocks. The filesystem on /dev/testvg/testlv is now 786432 blocks long. [root@centos ~]# lvreduce testlv -L 3G Path required for Logical Volume "testlv" Please provide a volume group name Run `lvreduce --help‘ for more information. [root@centos ~]# lvreduce -L 3G /dev/testvg/testlv WARNING: Reducing active logical volume to 3.00 GiB THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce testlv? [y/n]: y Size of logical volume testvg/testlv changed from 6.00 GiB (1536 extents) to 3.00 GiB (768 extents). Logical volume testlv successfully resized [root@centos ~]# df -lh Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_centos-lv_root 47G 4.7G 40G 11% / tmpfs 495M 72K 495M 1% /dev/shm /dev/sda1 477M 29M 424M 7% /boot #用pedisplay查出内个硬盘的快是free的 [root@centos ~]# pvdisplay --- Physical volume --- PV Name /dev/sdb1 VG Name testvg PV Size 2.01 GiB / not usable 3.16 MiB Allocatable yes PE Size 4.00 MiB Total PE 513 Free PE 513 Allocated PE 0 PV UUID QsN7uK-DTsA-IVdF-2TFY-jjcs-dN4E-UPa9XP --- Physical volume --- PV Name /dev/sdb3 VG Name testvg PV Size 4.01 GiB / not usable 2.54 MiB Allocatable yes PE Size 4.00 MiB Total PE 1025 Free PE 257 Allocated PE 768 PV UUID 2XqZ73-EBnb-yJF9-mIQQ-8VRg-46h3-T1fwLW --- Physical volume --- PV Name /dev/sdb2 VG Name testvg PV Size 3.01 GiB / not usable 2.79 MiB Allocatable yes PE Size 4.00 MiB Total PE 770 Free PE 770 Allocated PE 0 PV UUID BRUkrH-rSgS-a3VD-2KRC-yxHV-Cd76-eI6MX4 --- Physical volume --- PV Name /dev/sda2 VG Name vg_centos PV Size 49.51 GiB / not usable 3.00 MiB Allocatable yes (but full) PE Size 4.00 MiB Total PE 12674 Free PE 0 Allocated PE 12674 PV UUID CbCr1K-jw10-L3fC-Bsxm-Owql-zxQd-60cNab #从vg移除硬盘, 不能直接reduce vg先用用pe移除硬盘块数据 [root@centos ~]# vgreduce testvg /dev/sdb1 Physical volume "/dev/sdb3" still in use [root@centos ~]# pvmove /dev/sdb1 No data to move for testvg [root@centos ~]# pvmove /dev/sdb2 /dev/sdb2: Moved: 0.5% /dev/sdb2: Moved: 25.5% /dev/sdb2: Moved: 51.0% /dev/sdb2: Moved: 77.0% /dev/sdb2: Moved: 100.0% 再reduce [root@centos ~]# vgreduce testvg /dev/sdb1 Removed "/dev/sdb1" from volume group "testvg" [root@centos ~]# vgreduce testvg /dev/sdb2 Removed "/dev/sdb2" from volume group "testvg" [root@centos ~]# vgreduce testvg /dev/sdb3
3. lv的正式设备文件是在/dev/dm-*, 有两个符号连接文件指向这个文件/dev/vg名字/lv名字 和/dev/mapper/vg名字-lv名字
[root@centos ~]# ll /dev/testvg/testlv lrwxrwxrwx. 1 root root 7 Sep 23 11:12 /dev/testvg/testlv -> ../dm-2 [root@centos ~]# ll /dev/mapper/testvg-testlv lrwxrwxrwx. 1 root root 7 Sep 23 11:12 /dev/mapper/testvg-testlv -> ../dm-2
补充:snapshot
snapshot就是快照的意思, 它是实现来相同逻辑卷上的"备份"功能, 需要注意的是, snapshot不能取代一般意义上的备份.
快照的创建方式和创建lv一样, 只是要添加-s来指定快照卷.
接着上面的立即来创建个128M快照卷, 并且挂载到/snap
[root@centos ~]# lvcreate -L 128M -s -n lvsnap /dev/testvg/testlv Logical volume "lvsnap" created [root@centos ~]# mount /dev/testvg/lvsnap /snap
注意: 创在快照卷的时候, 最好停止在lv上的所有操作, 以免数据混乱