Linux文件系统管理―LVM

1.LVM的基本简介

       LVM：logical Volume Manager，逻辑卷管理，其目的在于可以弹性调整文件系统容量。LVM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，它可以整合多个物理分区在一起，让这些分区看起来像一个磁盘，而且，还可以将其他物理分区添加LVM中或从这个LVM管理的磁盘中删除。

2.LVM基本术语

       PV：Physical Volume物理卷，就是指硬盘分区或从逻辑上与磁盘分区具有同样功能的设备(如RAID)，是LVM的基本存储逻辑块，但和基本的物理存储介质（如分区、磁盘等）比较，却包含有与LVM相关的管理参数。注意：需要将分区标识符改为8e（LVM的标识符），然后用pvcreate

命令创建pv。

       VG：Volume Group卷组类似于非LVM系统中的物理硬盘，其由物理卷组成。可以在卷组上创建一个或多个“LVM分区”（逻辑卷），LVM卷组由一个或多个物理卷组成。

       PE：每一个物理卷被划分为称为PE(Physical Extents)的基本单元，具有唯一编号的PE是可以被LVM寻址的最小单元。PE的大小是可配置的，默认为4MB。

       LV：从VG中划分的逻辑分区。

3.LVM的创建与管理

创建分区：使用fdisk命令创建分区，调整分区标识符为8e。

[root@magedu ~]# 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    l   logical (5 or over)    p   primary partition (1-4) l First cylinder (7859-15665, default 7859):  Using default value 7859 Last cylinder, +cylinders or +size{K,M,G} (7859-15665, default 15665): +5G Command (m for help): n Command action    l   logical (5 or over)    p   primary partition (1-4) l First cylinder (8513-15665, default 8513):  Using default value 8513 Last cylinder, +cylinders or +size{K,M,G} (8513-15665, default 15665): +5G Command (m for help): P Disk /dev/sda: 128.8 GB, 128849018880 bytes 255 heads, 63 sectors/track, 15665 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: 0x00051a06    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        7859    62914560   8e  Linux LVM /dev/sda3            7859       15665    62708728+   5  Extended /dev/sda5            7859        8512     5252224+  83  Linux /dev/sda6            8513        9166     5253223+  83  Linux Command (m for help): t Partition number (1-6): 5 Hex code (type L to list codes): 8e Changed system type of partition 5 to 8e (Linux LVM) Command (m for help): t Partition number (1-6): 6 Hex code (type L to list codes): 8e Changed system type of partition 6 to 8e (Linux LVM) Command (m for help): p Disk /dev/sda: 128.8 GB, 128849018880 bytes 255 heads, 63 sectors/track, 15665 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: 0x00051a06    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        7859    62914560   8e  Linux LVM /dev/sda3            7859       15665    62708728+   5  Extended /dev/sda5            7859        8512     5252224+  8e  Linux LVM /dev/sda6            8513        9166     5253223+  8e  Linux LVM

创建PV：pvcreate  /dev/devices，使用pvdisplay查看pv详细信息

[root@magedu ~]# pvcreate /dev/sda5 /dev/sda6   Physical volume "/dev/sda5" successfully created   Physical volume "/dev/sda6" successfully created [root@magedu ~]# pvdisplay /dev/sda5 /dev/sda6   "/dev/sda5" is a new physical volume of "5.01 GiB"   --- NEW Physical volume ---   PV Name               /dev/sda5   VG Name                  PV Size               5.01 GiB   Allocatable           NO   PE Size               0      Total PE              0   Free PE               0   Allocated PE          0   PV UUID               L8WHe3-EdsZ-aC6K-RJUW-8kkL-D8wj-RiwkUv       "/dev/sda6" is a new physical volume of "5.01 GiB"   --- NEW Physical volume ---   PV Name               /dev/sda6   VG Name                  PV Size               5.01 GiB   Allocatable           NO   PE Size               0      Total PE              0   Free PE               0   Allocated PE          0   PV UUID               EcvE1Y-5wXl-t5Kc-M48F-Nrqw-R2hL-xi0hch

创建VG：vgcreate  VolumeGroupName  PhysicalDevicePath 

[root@magedu ~]# vgcreate myvg /dev/sda5 /dev/sda6   Volume group "myvg" successfully created [root@magedu ~]# vgdisplay myvg   --- Volume group ---   VG Name               myvg   System ID                Format                lvm2   Metadata Areas        2   Metadata Sequence No  1   VG Access             read/write   VG Status             resizable   MAX LV                0   Cur LV                0   Open LV               0   Max PV                0   Cur PV                2   Act PV                2   VG Size               10.02 GiB   PE Size               4.00 MiB   Total PE              2564   Alloc PE / Size       0 / 0      Free  PE / Size       2564 / 10.02 GiB   VG UUID               mDpNg3-cUa0-AQ2F-doM2-9wmj-fc6t-Q2XqiH

创建LV：lvcreate  -L #[mMgGtT] -n NAME VolumeGroup

[root@magedu ~]# lvcreate -L 10 -n mylv myvg   Rounding up size to full physical extent 12.00 MiB   Logical volume "mylv" created [root@magedu ~]# lvdisplay /dev/myvg/mylv    --- Logical volume ---   LV Path                /dev/myvg/mylv   LV Name                mylv   VG Name                myvg   LV UUID                yfJqxR-ao9l-uR9p-OcEb-Xdi4-pJ2d-7bYO5A   LV Write Access        read/write   LV Creation host, time magedu, 2015-08-18 13:21:49 +0800   LV Status              available   # open                 0   LV Size                12.00 MiB   Current LE             3   Segments               1   Allocation             inherit   Read ahead sectors     auto   - currently set to     256   Block device           253:4

LV格式化及挂载：lv需要先格式化才能存储

[root@magedu ~]# mke2fs -t ext4 /dev/myvg/mylv  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 3072 inodes, 12288 blocks 614 blocks (5.00%) reserved for the super user First data block=1 Maximum filesystem blocks=12582912 2 block groups 8192 blocks per group, 8192 fragments per group 1536 inodes per group Superblock backups stored on blocks:  8193 Writing inode tables: done                             Creating journal (1024 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 32 mounts or 180 days, whichever comes first.  Use tune2fs -c or -i to override. [root@magedu ~]# mkdir /tmp/lvtest [root@magedu ~]# mount /dev/myvg/mylv /tmp/lvtest/ [root@magedu ~]# mount /dev/mapper/vg0-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) /dev/sda1 on /boot type ext4 (rw) /dev/mapper/vg0-usr on /usr type ext4 (rw) /dev/mapper/vg0-var on /var type ext4 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) /dev/mapper/myvg-mylv on /tmp/lvtest type ext4 (rw)

扩展逻辑卷：

       lvextend -L [+]#[mMgGtT] /dev/VG_NAME/LV_NAME

       resize2fs /dev/VG_NAME/LV_NAME

缩减逻辑卷：

       umount /dev/VG_NAME/LV_NAME

       e2fsck -f /dev/VG_NAME/LV_NAME

       resize2fs /dev/VG_NAME/LV_NAME #[mMgGtT]

       lvreduce -L [-]#[mMgGtT] /dev/VG_NAME/LV_NAME