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

<ditaa round noedgesep>

   +--------+       +--------+
   |        |       |        |
   |  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
  1. 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.

  2. 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  
     

  3. 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
     

  4. 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
     

  5. 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
     

• https://www.thegeekdiary.com/redhat-centos-a-beginners-guide-to-lvm-logical-volume-manager/
• https://www.digitalocean.com/community/tutorials/an-introduction-to-lvm-concepts-terminology-and-operations
• https://www.thegeekdiary.com/centos-rhel-how-to-add-physical-volume-pv-to-a-volume-group-vg-in-lvm/
• https://pve.proxmox.com/wiki/Resize_disks