LVM 學習筆記 --转载　

3.4 創建物理卷的范例:

直接在硬盤設備上創建物理卷(PV):

pvcreate /dev/sdb;

pvcreate /dev/sdc;

pvcreate /dev/sdd;

pvcreate /dev/sde;

在磁盤分區(類型8e)上創建物理卷(PV):

pvcreate /dev/hda1;

pvcreate /dev/hdb1;

pvcreate /dev/hdc1;

pvscan; #掃描看看剛創建的PV;

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PV /dev/hda1 lvm2 [80.00 GB]

PV /dev/hdc1 lvm2 [80.00 GB]

PV /dev/hdb1 lvm2 [80.00 GB]

Total: 3 [240.00 GB] / in use: 0 [0 ] / in no VG: 3 [240.00 GB]

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pvdisplay /dev/hda1; #顯示物理卷信息;

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--- Physical volume ---

PV Name /dev/hda1

VG Name vg1

PV Size 80.00 GB / not usable 0

Allocatable yes

PE Size (KByte) 4096

Total PE 20479

Free PE 20479

Allocated PE 0

PV UUID sfEXEg-xYSz-NE3C-Timx-s0og-tyAh-Rgb3s6

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3.5 創建卷組的范例:

vgcreate vg1 /dev/hda1; #創建包含一個物理卷的卷組;

vgcreate vg2 /dev/hdb1 /dev/hdc1; #一個卷組可以包含多個物理卷;

vgscan; #掃描看看剛創建的卷組;

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Reading all physical volumes. This may take a while...

Found volume group "vg2" using metadata type lvm2

Found volume group "vg1" using metadata type lvm2

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vgdisplay -v vg2; #顯示卷組vg2的信息;

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Using volume group(s) on command line

Finding volume group "vg2"

--- Volume group ---

VG Name vg2

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 159.99 GB

PE Size 4.00 MB

Total PE 40958

Alloc PE / Size 0 / 0

Free PE / Size 40958 / 159.99 GB

VG UUID m2BEoc-liXS-h3dn-L4tH-ORF7-bG5p-Yx052h

--- Physical volumes ---

PV Name /dev/hdb1

PV UUID 6rdZod-Cprh-a9tS-zCK2-5DVx-hkFC-7ndR04

PV Status allocatable

Total PE / Free PE 20479 / 20479

PV Name /dev/hdc1

PV UUID 1coCsZ-BFCW-kYmJ-uCfG-jtol-WqjC-auA4zX

PV Status allocatable

Total PE / Free PE 20479 / 20479

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vgextend vg1 /dev/hdd1; #將物理卷/dev/hdd添加到卷組vg1中;

pvmove /dev/hdd1; #準備從卷組vg1中移除物理卷/dve/hdd,先騰空該物理卷的數據;

vgreduce vg1 /dev/hdd1; #將物理卷/dev/hdd移出卷組vg1;

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3.6 創建邏輯卷的范例:

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lvcreate -L 100M -n lv1 vg1;

lvcreate -L 500M -n lv2 vg1;

lvcreate -L 100G -n lv1 vg2;

lvcreate -L 500M -n lv2 vg2;

ls -l /dev/vg*; #創建邏輯卷(LV)後,會自動產生設備節點;

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/dev/vg1:

total 0

lrwxrwxrwx 1 root root 19 Aug 8 01:08 lv1 -> /dev/mapper/vg1-lv1

lrwxrwxrwx 1 root root 19 Aug 8 01:09 lv2 -> /dev/mapper/vg1-lv2

/dev/vg2:

total 0

lrwxrwxrwx 1 root root 19 Aug 8 01:08 lv1 -> /dev/mapper/vg2-lv1

lrwxrwxrwx 1 root root 19 Aug 8 01:10 lv2 -> /dev/mapper/vg2-lv2

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lvscan; #掃描看看剛創建的邏輯卷;

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ACTIVE '/dev/vg2/lv1' [100.00 GB] inherit

ACTIVE '/dev/vg2/lv2' [500.00 MB] inherit

ACTIVE '/dev/vg1/lv1' [100.00 MB] inherit

ACTIVE '/dev/vg1/lv2' [500.00 MB] inherit

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lvdisplay /dev/vg2/lv1; #顯示邏輯卷信息;

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--- Logical volume ---

LV Name /dev/vg2/lv1

VG Name vg2

LV UUID 0Y3o6N-pVlw-gFd9-8zSH-nS0D-27eH-2u4GU4

LV Write Access read/write

LV Status available

# open 0

LV Size 100.00 GB

Current LE 25600

Segments 2

Allocation inherit

Read ahead sectors 0

Block device 253:1

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lvdisplay vg2; #顯示卷組vg2中的所有邏輯卷信息;

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--- Logical volume ---

LV Name /dev/vg2/lv1

VG Name vg2

LV UUID 0Y3o6N-pVlw-gFd9-8zSH-nS0D-27eH-2u4GU4

LV Write Access read/write

LV Status available

# open 0

LV Size 100.00 GB

Current LE 25600

Segments 2

Allocation inherit

Read ahead sectors 0

Block device 253:0

--- Logical volume ---

LV Name /dev/vg2/lv2

VG Name vg2

LV UUID UkUiTC-BO5l-3om3-VY1N-6pG2-AWpe-6zKV8X

LV Write Access read/write

LV Status available

# open 0

LV Size 500.00 MB

Current LE 125

Segments 1

Allocation inherit

Read ahead sectors 0

Block device 253:1

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擴大空間:

lvextend -L +500M vg1/lv1; #添加500M空間到邏輯卷vg1/lv1;

e2fsck -f /dev/vg1/lv1; #先掃描一下掃描文件系統;

resize2fs /dev/vg1/lv1; #擴大文件系統;

縮小空間:

e2fsck -f /dev/vg1/lv1; #先掃描一下掃描文件系統;

resize2fs /dev/vg1/lv1 700M; #縮小空間,新空間等于700M;

lvreduce -L -200M vg1/lv1; #邏輯卷空間減少200M(因為原先的總空間為900M);

lvreduce -L 700M vg1/lv1; #也可以直接將邏輯卷空間變更為700M;

resize2fs /dev/vg1/lv1; #重新調整文件系統的空間;

注意:

可以不創建文件系統而直接使用邏輯卷LV,直接進行數據讀寫操作以提高性能. 也就是說可以

將邏輯卷當作裸设备(raw device)來使用,例如有些數據庫系統就是利用這種方式來儲存資料.

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3.7 其他LVM的操作范例:

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如欲保存數據,需先騰空相關物理卷的數據,例如:

pvmove /dev/hda1; #騰空物理卷/dev/hda數據;

先刪除卷組中的所有邏輯卷:

lvremove vg1/lv1; #刪除邏輯卷vg1/lv1;

lvremove /dev/vg1/lv2; #刪除邏輯卷vg1/lv2;

lvremove vg2/lv1; #刪除邏輯卷vg2/lv1;

將物理卷移出卷組:

vgreduce vg2 /dev/hdb1; #從卷組中移出物理卷;

將物理卷加入卷組:

vgextend vg2 /dev/hdb1; #將物理卷添加到卷組;

如果要刪除卷組,請按如下步驟:

vgchange -a n vg1; #刪除卷組前需要先停止該卷組的活動狀態;

vgremove vg1; #然后再刪除卷組;

注意: 如要刪除整個卷組,需先刪除該卷組的所有邏輯卷;

最后刪除物理卷:

pvremove /dev/hda1; #此命令只在LVM2版本中才有;

維護操作步驟:

vgscan; #掃描卷組的物理卷和邏輯卷狀態信息;

vgchange -ay; #啟動LVM;

vgchange -an; #停止LVM

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3.8 LVM快照

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快照(snapshot)是LVM所提供的一個非常有用的特性. 利用快照您可以凍結一個正在使用中的

邏輯卷,然后制作一份凍結時刻的備份,這個備份是具有一致性的. 快照是特殊類型的邏輯卷,

它含有創建時刻所指定的原始邏輯卷的完整數據,因此您可以操作快照而無需擔心數據的變更

令備份失效.

lsmod | grep dm; #使用snapshot需要內核模塊dm-snapshot;

modprobe dm-snapshot; #如有需要,必須先加載此模塊;

建立邏輯卷vg1/lv1的快照:

lvcreate -L500M -s -n sh1 vg1/lv1;

lvscan; #看看剛創建的快照;

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ACTIVE Original '/dev/vg1/lv1' [1.00 GB] inherit

ACTIVE '/dev/vg1/lv2' [2.00 GB] inherit

ACTIVE '/dev/vg1/lv3' [3.00 GB] inherit

ACTIVE Snapshot '/dev/vg1/sh1' [500.00 MB] inherit

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快照卷無需做格式化步驟,可以直接將快照卷掛載,卸載等操作,而且操作完成後,可以立即刪除

快照,因為快照不會自動更新,長久保留是沒有意義的:

lvremove /dev/vg1/sh1; #刪除快照;

注意: 創建快照卷的容量必須大于原始卷的實際數據總量(通常是1.1倍);

通常創建快照卷的主要目的是做備份用途, 可以寫一個簡單的備份腳本來自動創建快照, 然后

掛載進行備份, 備份完成後又自動卸載和刪除. 因為快照的創建速度非常快, 所以使用快照來

操作備份作業不僅可以解決一致性問題, 而且可以減少備份時間. 請參考如下代碼:

vi snapshot_backup.sh; #建立備份腳本;

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#!/bin/bash

today=`date "+%Y%m%d"`;

lvcreate -L1G -s -n sh1 /dev/vg1/lv1;

mount /dev/vg1/sh1 /disk/vg1/sh1;

tar -zcvf /tmp/snapshot_backup_$today.tar.gz /disk/vg1/sh1/*;

umount /dev/vg1/sh1;

lvremove -f /dev/vg1/sh1;

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chmod 755 snapshot_backup.sh; #設置運行權限;

可以將此備份腳本設置成每天定時運行,就可當成是一個完整備份的方案.