LVM (Logical Volume Management) 概念與基本語法

   +--------+       +--------+
   |        |       |        |
   |  File  |       |  File  |
   | System |       | System |
   |    {s} |       |    {s} |
   +--------+       +--------+
       |                |
   +---+----+       +---+----+
   |        |       |        |
   | Logical|       | Logical|
   | Volume |       | Volume |
   |    {s} |       |    {s} |
   +----+---+       +----+---+
        |                |
        +-+            +-+
          |            |
       +--+------------+--+
       |                  |
       |   Volume Group   |
       |               {s}|
       +---------+--------+
                 |
      +----------+----------+
      |          |          |
 +----+---+ +----+---+ +----+---+
 |Physical| |Physical| |Physical|
 | Volume | | Volume | | Volume |
 |     {s}| |     {s}| |     {s}|
 +--------+ +--------+ +--------+

</ditaa>

Physical Volume (PV) : 就是實體區, 可以是一顆硬碟(Disk)或是一個分割區(Partition) 相關指令 : pvcreate, pvdisplay, pvs, pvchange, pvscan
Volume Group (VG) : 就是整合實體區(PV)與邏輯區(LV), 相關指令 : vgcreate, vgdisplay, vgs, vgextend, vgscan
Logical Volume(LV) : 就是邏輯區, 可以建立一個邏輯來格式化成檔案系統(File System), 相關指令 : lvcreate, lvdisplay, lvs, lvscan, lvresize, lvextend

使用 LVM 的好處是讓檔案系統可以更有彈性的來調整, 不必然受限於實體的硬碟大小

例如原有硬碟(或分割)大小空間滿了, 想要加一顆硬碟(或分割)後, 讓原本資料目錄的空間變大, 以下是在 KVM 虛擬環境先將一顆 10G 的 QEMU 虛擬硬碟加上 10G (變成 20G)後, 透過一系列的程序讓 / 空間多出 10G 的作法

將加上的 10G 空間, 使用 parted 指令建立新的分割區參考指令 print , mkpart primary , set <編號> lvm 完成內容

(parted) print
Model: QEMU QEMU HARDDISK (scsi)
磁碟 /dev/sda：21.5GB
磁區大小 (邏輯/物理)：512B/512B
分割區：msdos

編號  起始點  結束點  大小    類型     檔案系統  旗標
 1    1049kB  525MB   524MB   primary  ext4      啟動
 2    525MB   10.7GB  10.2GB  primary            lvm
 3    10.7GB  21.5GB  10.7GB  primary            lvm

[root@pve-svn ~]# fdisk -l /dev/sda

Disk /dev/sda: 21.5 GB, 21474836480 bytes
64 heads, 32 sectors/track, 20480 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000a3b61

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           2         501      512000   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2             502       10240     9972736   8e  Linux LVM
Partition 2 does not end on cylinder boundary.
/dev/sda3           10241       20480    10485760   8e  Linux LVM
Partition 3 does not end on cylinder boundary.

用 pvcreate 命令將新產生的分割區 /dev/sda3 建立為 PV 執行語法

pvcreate /dev/sda3

[root@pve-svn ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               VolGroup
  PV Size               9.51 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              2434
  Free PE               0
  Allocated PE          2434
  PV UUID               0gGDwt-cU4B-ohe4-zLG8-VB3V-SDzX-aUSQ6S

  "/dev/sda3" is a new physical volume of "10.00 GiB"
  --- NEW Physical volume ---
  PV Name               /dev/sda3
  VG Name
  PV Size               10.00 GiB
  Allocatable           NO
  PE Size               0
  Total PE              0
  Free PE               0
  Allocated PE          0
  PV UUID               Zotmmo-VZng-6TfS-pJKA-k3TR-O87q-vAPurv

[root@pve-svn ~]# pvscan
  PV /dev/sda2   VG VolGroup        lvm2 [9.51 GiB / 0    free]
  PV /dev/sda3                      lvm2 [10.00 GiB]
  Total: 2 [19.51 GiB] / in use: 1 [9.51 GiB] / in no VG: 1 [10.00 GiB]

[root@pve-svn ~]# pvs
  PV         VG       Fmt  Attr PSize  PFree
  /dev/sda2  VolGroup lvm2 a--u  9.51g     0
  /dev/sda3           lvm2 ---- 10.00g 10.00g

將剛產生的 PV /dev/sda3 以 vgextend 命令來加入現有的 VG - VolGroup 執行語法

[root@pve-svn ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup
  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       2434 / 9.51 GiB
  Free  PE / Size       0 / 0
  VG UUID               eK3ash-hbJh-yrjl-Gbci-8gyc-ueCE-4oVjiZ

[root@pve-svn ~]# vgextend VolGroup /dev/sda3
  Volume group "VolGroup" successfully extended

[root@pve-svn ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup
  System ID
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  5
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               19.50 GiB
  PE Size               4.00 MiB
  Total PE              4993
  Alloc PE / Size       2434 / 9.51 GiB
  Free  PE / Size       2559 / 10.00 GiB
  VG UUID               eK3ash-hbJh-yrjl-Gbci-8gyc-ueCE-4oVjiZ

[root@pve-svn ~]# vgs
  VG       #PV #LV #SN Attr   VSize  VFree
  VolGroup   2   2   0 wz--n- 19.50g 10.00g

使用 lvextend 或 lvresize 來加大現有 lv_root 的 LV 執行語法

[root@pve-svn ~]# lvdisplay
  --- Logical volume ---
  LV Path                /dev/VolGroup/lv_root
  LV Name                lv_root
  VG Name                VolGroup
  LV UUID                JbZGhn-aEuR-sohP-RSGc-FF09-hk9V-Qi5dXL
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2013-05-23 11:46:40 +0800
  LV Status              available
  # open                 1
  LV Size                7.54 GiB
  Current LE             1930
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0

  --- Logical volume ---
  LV Path                /dev/VolGroup/lv_swap
  LV Name                lv_swap
  VG Name                VolGroup
  LV UUID                5SRhkK-6vuF-SAe8-g7P1-FhJp-E0YM-rrBcvj
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2013-05-23 11:46:46 +0800
  LV Status              available
  # open                 1
  LV Size                1.97 GiB
  Current LE             504
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

[root@pve-svn ~]# lvextend --size +10G /dev/VolGroup/lv_root
  Insufficient free space: 2560 extents needed, but only 2559 available
[root@pve-svn ~]# lvextend -l +2560 /dev/VolGroup/lv_root
  Insufficient free space: 2560 extents needed, but only 2559 available
[root@pve-svn ~]# lvextend -l +2559 /dev/VolGroup/lv_root
  Size of logical volume VolGroup/lv_root changed from 7.54 GiB (1930 extents) to 17.54 GiB (4489 extents).
  Logical volume lv_root successfully resized.

[root@pve-svn ~]# lvresize -l +100%FREE /dev/VolGroup/lv_root


[root@pve-svn ~]# vgs -o +lv_size,lv_name
  VG       #PV #LV #SN Attr   VSize  VFree LSize  LV
  VolGroup   2   2   0 wz--n- 19.50g    0  17.54g lv_root
  VolGroup   2   2   0 wz--n- 19.50g    0   1.97g lv_swap

[root@pve-svn ~]# lvs
  LV      VG       Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  lv_root VolGroup -wi-ao---- 17.54g
  lv_swap VolGroup -wi-ao----  1.97g

透過 resize2fs 讓 LV 增加的空間實際生效執行語法

[root@pve-svn ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                      7.3G  1.8G  5.2G  26% /
tmpfs                 498M     0  498M   0% /dev/shm
/dev/sda1             477M  126M  326M  28% /boot

[root@pve-svn ~]# resize2fs /dev/VolGroup/lv_root
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/VolGroup/lv_root is mounted on /; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 2
Performing an on-line resize of /dev/VolGroup/lv_root to 4596736 (4k) blocks.
The filesystem on /dev/VolGroup/lv_root is now 4596736 blocks long.

[root@pve-svn ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       18G  1.8G   15G  12% /
tmpfs                 498M     0  498M   0% /dev/shm
/dev/sda1             477M  126M  326M  28% /boot

參考網址

lvm