一、簡介
LVM是 Logical Volume Manager（邏輯卷管理）的簡寫，它是基於內核的一種邏輯卷管理器，LVM適合於管理大存儲設備，並允許用戶動態調整文件系統大小。此外，LVM的快照功能可以幫助我們快速備份數據。LVM爲我們提供了邏輯概念上的磁盤，使得文件系統不在關心底層物理磁盤的概念。並且它是Linux環境下對磁盤分區進行管理的一種機制，使用lvm用戶可以在無需停機的情況下方便地調整各個分區大小。
看圖識LVM
二、LVM基本概念
1、Physical Volume(PV),物理卷：創建分區時，標記分區類型爲8e後，就可以將該分區做成物理卷供LVM使用了。可以用任意塊設備做成物理卷，單個分區、整塊硬盤、RAID設備都可以。
2、Volume Group(VG),卷組：顧名思義，就是將一個或多個PV組合爲一個卷組，以PE爲存儲單位。一個VG至少包含一個PV，VG可以創建多個。
3、Physical Extent(PE)，物理區域：PE是整個LVM中可分配的最小存儲單元，大小在創建卷組時指定且確定後不能更改；同一卷組的PE大小需一致。新的PV加入卷組後，PE的大小會自動更改爲原卷組PE的大小。
4、Logical Volume(LV),邏輯卷：建立在卷組的基礎上，卷組中空閒的PE可分配給LV使用，創建LV後可通過增加或減少PE來動態擴展和縮小空間大小。LV可以直接創建文件系統並掛載使用。兩種寫入模式：線性模式（linear）、交錯模式（triped）。
三、LVM常用管理工具
準備工作：
# fdisk /dev/sda #創建分區並調整分區格式（lvm格式爲8e）
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
e extended
p primary partition (1-4)
e
Selected partition 4
First cylinder (1632-26108, default 1632):
Using default value 1632
Last cylinder, +cylinders or +size{K,M,G} (1632-26108, default 26108):
Using default value 26108
Command (m for help): n
First cylinder (1632-26108, default 1632):
Using default value 1632
Last cylinder, +cylinders or +size{K,M,G} (1632-26108, default 26108): +5G
Command (m for help): n
First cylinder (2286-26108, default 2286):
Using default value 2286
Last cylinder, +cylinders or +size{K,M,G} (2286-26108, default 26108): +5G
Command (m for help): n
First cylinder (2940-26108, default 2940):
Using default value 2940
Last cylinder, +cylinders or +size{K,M,G} (2940-26108, default 26108): +5G
Command (m for help): n
First cylinder (3594-26108, default 3594): +5G
Value out of range.
First cylinder (3594-26108, default 3594):
Using default value 3594
Last cylinder, +cylinders or +size{K,M,G} (3594-26108, default 26108): +5G
Command (m for help): t
Partition number (1-8): 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 (1-8): 6
Hex code (type L to list codes): 8e
Changed system type of partition 6 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-8): 7
Hex code (type L to list codes): 8e
Changed system type of partition 7 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-8): 8
Hex code (type L to list codes): 8e
Changed system type of partition 8 to 8e (Linux LVM)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
# kpartx -af /dev/sda
# partx -a /dev/sda （centos6.7需要這兩步才能讀取硬盤）
# cat /proc/partitions （查看磁盤情況）
major minor #blocks name
8 0 209715200 sda
8 1 819200 sda1
8 2 10240000 sda2
8 3 2048000 sda3
8 4 31 sda4
8 5 5246007 sda5
8 6 5253223 sda6
8 7 5253223 sda7
8 8 5253223 sda8
# fdisk -l
Disk /dev/sda: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 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: 0x000711d9
Device Boot Start End Blocks Id System
/dev/sda1 * 1 103 819200 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2 103 1377 10240000 83 Linux
/dev/sda3 1377 1632 2048000 82 Linux swap / Solaris
/dev/sda4 1632 26108 196604286 5 Extended
/dev/sda5 1632 2285 5246007 8e Linux LVM
/dev/sda6 2286 2939 5253223+ 8e Linux LVM
/dev/sda7 2940 3593 5253223+ 8e Linux LVM
/dev/sda8 3594 4247 5253223+ 8e Linux LVM1、物理卷(PV)的常用管理命令
pvcreate #創建一個物理卷 pvchange #修改物理卷的屬性 pvresize #調整一個PV的大小 pvremove #刪除一個PV pvdisplay #顯示PV的屬性信息 pvmove #移動PE到指定物理卷 pvscan #搜索所有磁盤上的物理卷 pvs #顯示PV的簡要信息
示例1：創建4個PV
# pvcreate /dev/sda{5..8}
Physical volume "/dev/sda5" successfully created
Physical volume "/dev/sda6" successfully created
Physical volume "/dev/sda7" successfully created
Physical volume "/dev/sda8" successfully created
# pvs #查看磁盤PV情況
PV VG Fmt Attr PSize PFree
/dev/sda5 lvm2 --- 5.00g 5.00g
/dev/sda6 lvm2 --- 5.01g 5.01g
/dev/sda7 lvm2 --- 5.01g 5.01g
/dev/sda8 lvm2 --- 5.01g 5.01g
# pvdisplay #查看PV詳細信息
"/dev/sda5" is a new physical volume of "5.00 GiB"
--- NEW Physical volume --- #新PV
PV Name /dev/sda5 #物理卷名稱
VG Name
PV Size 5.00 GiB #物理卷大小
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID F4waZ4-gQtM-lrZm-RN7O-1HFX-axqe-M5IdE0
"/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 fykqC3-4PPg-lgfR-iWQO-WzPK-goRT-W4S7uy
"/dev/sda7" is a new physical volume of "5.01 GiB"
--- NEW Physical volume ---
PV Name /dev/sda7
VG Name
PV Size 5.01 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID xakBcc-U6lL-vLC7-WIc1-X2Td-tetj-GKBlOu
"/dev/sda8" is a new physical volume of "5.01 GiB"
--- NEW Physical volume ---
PV Name /dev/sda8
VG Name
PV Size 5.01 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID OOr5Dh-i7ZW-UjsC-rTxW-MrnP-USMI-XQcmOO示例2：刪除PV
# pvmove /dev/sda5 /dev/sda6 #注意：兩個PV必須在同一卷組內 # pvremove /dev/sda5 #刪除PV前要確保該PV沒有在任何卷組中 Labels on physical volume "/dev/sda5" successfully wiped # pvs PV VG Fmt Attr PSize PFree /dev/sda6 lvm2 --- 5.01g 5.01g /dev/sda7 lvm2 --- 5.01g 5.01g /dev/sda8 lvm2 --- 5.01g 5.01g
2、卷組(VG)的常用管理命令
vgcreate #創建卷組 -l：設置可容納的LV最大數，默認爲255 -p：設置包含PV的最大數，默認爲255 -s：設置PE大小，默認爲4M vgextend #擴展VG大小 vgdisplay #顯示VG屬性信息 vgchange #修改VG屬性信息 vgreduce #縮減VG大小 vgremove #刪除VG vgscan #搜索所有磁盤上的卷組 vgs #顯示VG簡要信息 vgck #檢查VG元數據
示例1：創建一個卷組，要求PE大小爲8M，名稱爲bjwf,最大支持LV不能超過10個，包含的PV不能超過2個
# vgcreate -s 8M -l 10 -p 2 bjwf /dev/sda{7,8}
Volume group "bjwf" successfully created
# vgdisplay bjwf #查看VG屬性信息驗證結果
--- Volume group ---
VG Name bjwf #VG名稱
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 10 #可以看到，支持最大LV數爲10個
Cur LV 0
Open LV 0
Max PV 2 #支持最大PV數爲2個
Cur PV 2
Act PV 2
VG Size 10.02 GiB #卷組大小
PE Size 8.00 MiB #PE的大小
Total PE 1282
Alloc PE / Size 0 / 0
Free PE / Size 1282 / 10.02 GiB #剩餘容量
VG UUID 7q5Lka-cnTN-qqlh-eIg1-Fpr2-2IPY-yrHA1S示例2：擴展bjwf的大小
# vgextend bjwf /dev/sda6 #這塊由於此前定義了VG的最大PV數，所以無法擴展 No space for '/dev/sda6' - volume group 'bjwf' holds max 2 physical volume(s). Unable to add physical volume '/dev/sda6' to volume group 'bjwf'. # vgchange -p 3 bjwf #修改VG屬性 Volume group "bjwf" successfully changed # vgextend bjwf /dev/sda6 #擴展VG Volume group "bjwf" successfully extended #顯示成功 # vgdisplay bjwf #查看新擴展的VG --- Volume group --- VG Name bjwf System ID Format lvm2 Metadata Areas 3 Metadata Sequence No 3 VG Access read/write VG Status resizable MAX LV 10 Cur LV 0 Open LV 0 Max PV 3 #最大PV數已經改爲3個 Cur PV 3 Act PV 3 VG Size 15.02 GiB #VG大小也已經改變 PE Size 8.00 MiB Total PE 1923 Alloc PE / Size 0 / 0 Free PE / Size 1923 / 15.02 GiB VG UUID 7q5Lka-cnTN-qqlh-eIg1-Fpr2-2IPY-yrHA1S
示例3：縮減bjwf大小，然後刪除bjwf
# vgreduce bjwf /dev/sda8 #注意：把PV移除卷組時要保證該PV數據已經遷移或未使用 Removed "/dev/sda8" from volume group "bjwf" # vgchange -an bjwf #標記bjwf爲不可用狀態 0 logical volume(s) in volume group "bjwf" now active # vgremove bjwf #不論VG包含多少PV都可以刪除，前提是該VG上沒有任何LV，如果有就需要先刪除LV Volume group "bjwf" successfully removed # vgs #查看VG情況
3、邏輯卷（LV）的常用管理命令
lvcreate #創建LV -l：設置LV大小，以PE爲單位 -L：設置LV大小，以字節爲單位 -n：設置LV名稱 -p：設置LV權限讀寫權限，默認爲可讀可寫 -s：設置一個快照卷，對一個已存在的LV做快照 lvextend #擴展LV大小 lvreduce #縮減LV大小 lvchange #修改LV屬性信息 -ay：標記LV爲可用狀態 -an：標記LV爲不可用狀態 lvremove #刪除LV lvdisplay #顯示LV屬性信息 lvscan #搜索所有磁盤上的邏輯卷 lvs #顯示LV簡要信息
示例1：創建一個LV，要求大小爲10G，名稱爲mylv，指定卷組爲bjwf，並掛載到/data上
# lvcreate -L 10G -n mylv bjwf Logical volume "mylv" created. # lvdisplay #LV詳細情況 --- Logical volume --- LV Path /dev/bjwf/mylv #邏輯卷mylv的陸佳 LV Name mylv #邏輯卷名稱爲mylv VG Name bjwf #基於bjwf卷組 LV UUID gvQMEB-1Zzo-IVth-KV7v-O6QH-8Nxw-IK1RIf LV Write Access read/write LV Creation host, time mail.bjwf.com, 2016-02-01 17:16:57 +0800 LV Status available # open 0 LV Size 10.00 GiB Current LE 2560 Segments 2 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 # mke2fs -t ext4 /dev/bjwf/mylv #格式化mylv # mkdir /data #創建目錄 # mount /dev/bjwf/mylv /data #掛載到指定目錄 # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 9.5G 6.6G 2.5G 73% / tmpfs 3.9G 0 3.9G 0% /dev/shm /dev/sda1 772M 39M 693M 6% /boot /dev/mapper/bjwf-mylv 9.8G 23M 9.2G 1% /data #大小爲10G的/data
示例2：擴展mylv的大小，增加5G空間
# lvextend -L 15G /dev/bjwf/mylv #方法一,擴展物理邊界增加到15G # lvextend -L +5G /dev/bjwf/mylv #方法二,擴展物理邊界增加5G # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 9.5G 6.6G 2.5G 73% / tmpfs 3.9G 0 3.9G 0% /dev/shm /dev/sda1 772M 39M 693M 6% /boot /dev/mapper/bjwf-mylv 9.8G 23M 9.2G 1% /data #仍然爲10G，邏輯卷沒有增加 # resize2fs /dev/bjwf/mylv #擴展邏輯邊界。 注：只對ext文件系統使用。這裏也可以指定擴展邏輯邊界大小，默認物理邊界大小。 resize2fs 1.41.12 (17-May-2010) Filesystem at /dev/bjwf/mylv is mounted on /data; on-line resizing required old desc_blocks = 1, new_desc_blocks = 1 Performing an on-line resize of /dev/bjwf/mylv to 3932160 (4k) blocks. The filesystem on /dev/bjwf/mylv is now 3932160 blocks long. # lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert mylv bjwf -wi-ao---- 15.00g # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 9.5G 6.6G 2.5G 73% / tmpfs 3.9G 0 3.9G 0% /dev/shm /dev/sda1 772M 39M 693M 6% /boot /dev/mapper/bjwf-mylv 15G 25M 14G 1% /data #大小已經增加到15G
示例三：縮減mylv的大小，減少9G空間（縮減的順序與創建時的順序相反，也就是先卸載文件系統，縮減邏輯卷，縮減物理卷。縮減很危險，不到最後一步千萬不要縮減，縮減需要離線。）
# umount /data/ #卸載，住：卸載前先將數據拿走，血的教訓 # e2fsck -f /dev/bjwf/mylv #強制檢查 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/bjwf/mylv: 12/983040 files (0.0% non-contiguous), 100865/3932160 blocks # resize2fs /dev/bjwf/mylv 7G #縮減邏輯邊界至7G resize2fs 1.41.12 (17-May-2010) Resizing the filesystem on /dev/bjwf/mylv to 1835008 (4k) blocks. The filesystem on /dev/bjwf/mylv is now 1835008 blocks long. # lvreduce -L 7G /dev/bjwf/mylv #縮減物理邊界至7G WARNING: Reducing active logical volume to 7.00 GiB THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce mylv? [y/n]: y #確認，後果自負 Size of logical volume bjwf/mylv changed from 15.00 GiB (3840 extents) to 7.00 GiB (1792 extents). Logical volume mylv successfully resized # mount /dev/bjwf/mylv /data/ #重新掛載 # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda2 9.5G 6.6G 2.5G 73% / tmpfs 3.9G 0 3.9G 0% /dev/shm /dev/sda1 772M 39M 693M 6% /boot /dev/mapper/bjwf-mylv 6.8G 23M 6.4G 1% /data #已經縮減至7G
示例四：對mylv創建一個快照卷，快照恢復後，卸載快照卷並刪除
# lvcreate -L 50M -n mylv_snap -p r -s /dev/bjwf/mylv #對mylv做快照，首先要確定邏輯卷裏面暫用的空間大小小於50M，不然快照沒意義 Rounding up size to full physical extent 52.00 MiB Logical volume "mylv_snap" created. # lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync C onvert mylv bjwf owi-a-s--- 10.00g mylv_snap bjwf sri-a-s--- 52.00m mylv 0.00 #快照卷 # mkdir /snap #創建掛載點 # mount /dev/bjwf//mylv_snap /snap/ #掛載快照至指定目錄 mount: block device /dev/mapper/bjwf-mylv_snap is write-protected, mounting read-only # umount /snap/ #卸載，一定要確定數據是否移除 # lvremove /dev/bjwf/mylv_snap #刪除快照卷 Do you really want to remove active logical volume mylv_snap? [y/n]: y #確認 Logical volume "mylv_snap" successfully removed
示例五：刪除mylv
# lvchange -an /dev/bjwf/mylv #標記mylv爲不可用狀態 # lvremove /dev/bjwf/mylv #刪除LV Logical volume "mylv" successfully removed
以上乃是個人學習總結，如有錯誤或遺留問題，還望指正！！！！！！！！！！！！！！