LVM逻辑卷管理(Logical Volume Manager)
随着数据的逐渐增加,当初设计的磁盘大小已经满足不了现在的需求了,当磁盘面临着满盘时,运维人员如何解决问题?是换一个更大的磁盘,把原先的数据copy到现在更大的磁盘里面,继续撑一段时间,还是寻找其它方法?LVM的出现很好的解决了这一问题。LVM是linux环境下对磁盘分区进行管理的一种机制,是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。
LVM有两个特性
1、便捷的调整文件系统大小
2、支持快照snapshot
创建LVM的示意图
PV可以是硬盘的分区,PV组成了VG,在VG上面割取PE就组成了LV
物理卷physical volume (PV)
物理卷是硬盘分区,也可以是整个硬盘或已创建的Software RAID 卷。
卷组volume group (VG)
卷组是LVM 中最高抽象层,是由一个或多个物理卷所组成的存储器池。
物理块physical extent (PE)
物理卷按大小相等的“块”为单位存储,块的大小与卷组中逻辑卷块的大小相同。
逻辑块logical extent (LE)
逻辑卷按“块”为单位存储,在一卷组中的所有逻辑卷的块大小是相同的。
逻辑卷logical volume (LV)
逻辑卷相当于非LVM 系统中的分区,它在卷组上建立,是一个标准的块设备,可以在其上建立文件系统
从一块硬盘到能使用LV文件系统的步骤:
硬盘----分区----PV----VG----LV----格式化(LV为ext文件系统)----挂载
一、LVM的第一个特性,便捷的调整文件系统大小
1、PV的相关操作
先对硬盘进行分区
pvcreate 创建PV
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[root@Redhat6 ~]
# pvcreate /dev/sda5 /dev/sda6
Physical volume
"/dev/sda5"
successfully created
Physical volume
"/dev/sda6"
successfully created
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pvromve 移除PV
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[root@Redhat6 ~]
# pvremove /dev/sda5
Labels on physical volume
"/dev/sda5"
successfully wiped
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pvdisplay 显示PV的详细信息,用pvs也可以显示pv的信息
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[root@Redhat6 ~]
# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2
vg0 lvm2 a-- 59.99g 7.99g
/dev/sda5
lvm2 a-- 10.00g 10.00g
/dev/sda6
lvm2 a-- 10.00g 10.00g
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pvmove 移动pv,将此PV的数据转移至其它PV
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[root@Redhat6 ~]
# pvmove /dev/sda5 /dev/sda6 #把sda5的数据转移到sda6上面
/dev/sda5
: Moved: 100.0%
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2、VG的相关操作
vgcreate 创建vg,-s PE:指定PE大小,默认为4M
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[root@Redhat6 ~]
# vgcreate myvg /dev/sda5 /dev/sda6
Volume group
"myvg"
successfully created
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vgdisplay 显示VG的详细信息,用vgs也可以显示VG的信息
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[root@Redhat6 ~]
# vgdisplay
--- Volume group ---
VG Name myvg
System ID
Format lvm2
Metadata Areas 3
Metadata Sequence No 2
VG Access
read
/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 3
Act PV 3
VG Size 25.01 GiB
PE Size 4.00 MiB
Total PE 6402
Alloc PE / Size 0 / 0
Free PE / Size 6402 / 25.01 GiB
VG UUID cLkCtE-LB7X-SYCE-GcKF-I30f-pBYH-MTCLZC
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vgremove 移除vg,只需跟vg的名称即可
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[root@Redhat6 ~]
# vgremove myvg
Volume group
"myvg"
successfully removed
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vgextend vg的扩展,先必须添加其它的PV
首先准备好一个PV--->然后使用vgextend命令即可完成扩展
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[root@Redhat6 ~]
# pvcreate /dev/sda5 /dev/sda6 #创建PV
Physical volume
"/dev/sda5"
successfully created
Physical volume
"/dev/sda6"
successfully created
[root@Redhat6 ~]
# vgcreate myvg /dev/sda5 /dev/sda6 #创建VG
Volume group
"myvg"
successfully created
[root@Redhat6 ~]
# pvcreate /dev/sda3 #把另外一个分区创建为PV
Physical volume
"/dev/sda3"
successfully created
[root@Redhat6 ~]
# vgextend myvg /dev/sda3 #在myvg组里面扩展VG
Volume group
"myvg"
successfully extended
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vgreduce vg的缩减,
确定要移除的PV--->将此PV的数据转移至其它PV---->从卷组中将此PV移除
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[root@Redhat6 ~]
# pvs #查看PV,确定要移除哪个PV
PV VG Fmt Attr PSize PFree
/dev/sda2
vg0 lvm2 a-- 59.99g 7.99g
/dev/sda3
myvg lvm2 a-- 5.01g 5.01g
/dev/sda5
myvg lvm2 a-- 10.00g 3.00g
/dev/sda6
myvg lvm2 a-- 10.00g 10.00g
[root@Redhat6 ~]
# pvmove /dev/sda3 /dev/sda5 #把sda3的数据转移到sda5上面
/dev/sda3
: Moved: 100.0%
[root@Redhat6 ~]
# vgreduce myvg /dev/sda3 #从VG中把PV移除
Removed
"/dev/sda3"
from volume group
"myvg"
[root@Redhat6 ~]
# pvs
PV VG Fmt Attr PSize PFree
/dev/sda2
vg0 lvm2 a-- 59.99g 7.99g
/dev/sda3
lvm2 a-- 5.01g 5.01g
/dev/sda5
myvg lvm2 a-- 10.00g 3.00g
/dev/sda6
myvg lvm2 a-- 10.00g 10.00g
[root@Redhat6 ~]
#
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3、LV的相关操作
lvcreate 创建LV,相关参数:-l 指定PE个数,-L指定LV的大小,
-s创建一个快照卷,-n LV的名称
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[root@Redhat6 ~]
# lvcreate -L 5G -n lv1 myvg
Logical volume
"lv1"
created
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lvdisplay 显示LV的详细信息,用lvs也可以显示LV的信息
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[root@Redhat6 ~]
# lvdisplay
--- Logical volume ---
LV Path
/dev/myvg/lv1
LV Name lv1
VG Name myvg
LV UUID 7Ewvyg-pEFI-o4XL-kFDa-Jtvl-hmak-5fg3qT
LV Write Access
read
/write
LV Creation host,
time
Redhat6, 2013-07-23 05:42:33 +0800
LV Status available
# open 0
LV Size 5.00 GiB
#创建一个5G的lv
Current LE 1280
Segments 1
Allocation inherit
Read ahead sectors auto
- currently
set
to 256
Block device 253:4
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lvremove 移除lv,需要移除lv的设备文件:
/dev/myvg/lv1或者/dev/mapper/myvg-lv1
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[root@Redhat6 ~]
# lvremove /dev/myvg/lv1
Do you really want to remove active logical volume lv1? [y
/n
]: y
Logical volume
"lv1"
successfully removed
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lvextend 扩展LV
先确定要扩展多大-->确定当前VG有足够的空闲空间-->扩展(1、物理边界---2、逻辑边界)
当VG不够时,先增加PV,在扩展VG,最后在VG上面扩展LV。
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[root@Redhat6 ~]
# mke2fs -t ext4 /dev/myvg/lv1 #先把lv格式化
[root@Redhat6 ~]
# lvextend -L +4G /dev/myvg/lv1 #实现物理扩容
Extending logical volume lv1 to 9.00 GiB
#之前只有5G,现在扩了4G
Logical volume lv1 successfully resized
[root@Redhat6 ~]
# resize2fs /dev/myvg/lv1 #实现逻辑扩容
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on
/dev/myvg/lv1
to 2359296 (4k) blocks.
The filesystem on
/dev/myvg/lv1
is now 2359296 blocks long.
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lvreduce 缩小LV
先卸载--->然后减小逻辑边界---->最后减小物理边界--->在检测文件系统 ====谨慎用===
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[root@Redhat6 ~]
# umount /dev/mapper/myvg-lv1
[root@Redhat6 ~]
# e2fsck -f /dev/myvg/lv1
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/myvg/lv1
: 13
/589824
files (0.0% non-contiguous), 73829
/2359296
blocks
[root@Redhat6 ~]
# resize2fs /dev/myvg/lv1 7G #把lv减少到7G,减少了2G
resize2fs 1.41.12 (17-May-2010)
Resizing the filesystem on
/dev/myvg/lv1
to 524288 (4k) blocks.
The filesystem on
/dev/myvg/lv1
is now 524288 blocks long.
[root@Redhat6 ~]
# lvs #查看lv的大小发现并没有实际的减少
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv1 myvg -wi-a---- 9.00g
root vg0 -wi-ao--- 20.00g
swap vg0 -wi-ao--- 2.00g
usr vg0 -wi-ao--- 10.00g
var vg0 -wi-ao--- 20.00g
[root@Redhat6 ~]
# lvreduce -L -2G /dev/myvg/lv1 #减少lv的物理边界,指定减少2G
WARNING: Reducing active logical volume to 7.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv1? [y
/n
]: y
Reducing logical volume lv1 to 7.00 GiB
Logical volume lv1 successfully resized
[root@Redhat6 ~]
# lvs #查看lv的大小发现已经实际的减少了
LV VG Attr LSize Pool Origin Data% Move Log Cpy%Sync Convert
lv1 myvg -wi-a---- 7.00g
root vg0 -wi-ao--- 20.00g
swap vg0 -wi-ao--- 2.00g
usr vg0 -wi-ao--- 10.00g
var vg0 -wi-ao--- 20.00g
[root@Redhat6 ~]
# e2fsck -f /dev/myvg/lv1 #减少之后检查文件系统
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/myvg/lv1
: 13
/131072
files (0.0% non-contiguous), 43698
/524288
blocks
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二、LVM的第二个特性,在备份数据的时候创键快照卷
当需要备份LV里面的数据时,且LV的数据也在进行写操作时,这个时候创建快照就很有必要了,快照是一个访问LV里面数据的一个通道,他不会保存LV里面所有的数据,当LV某些PE里面数据变化时,快照保存之前PE的数据,未变化的PE将不会被保存。
步骤:
分区--->创建PV--->创建VG--->创建LV--->格式化LV为ext4--->挂载--->写入数据--->需要备份(创建快照)--->创建快照卷--->再次继续写入数据---->挂载快照卷--->备份之前的数据到快照卷里面--->卸载快照--->删除快照卷
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root@station128 ~]
# fdisk /dev/sda #先建立两个逻辑分区,大小为10G
Command (m
for
help): n
First cylinder (9165-15665, default 9165):
Using default value 9165
Last cylinder, +cylinders or +size{K,M,G} (9165-15665, default 15665): +10G
Command (m
for
help): t
Partition number (1-5): 5
Hex code (
type
L to list codes): 8e
#并改为LVM文件系统
Changed system
type
of partition 5 to 8e (Linux LVM)
Command (m
for
help): n
First cylinder (10471-15665, default 10471):
Using default value 10471
Last cylinder, +cylinders or +size{K,M,G} (10471-15665, default 15665): +10G
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): w
[root@Redhat6 ~]
# pvcreate /dev/sda5 /dev/sda6 #创建PV
Physical volume
"/dev/sda5"
successfully created
Physical volume
"/dev/sda6"
successfully created
[root@Redhat6 ~]
# vgcreate -s 8M myvg /dev/sda5 /dev/sda6 #创建VG,并指定PE为8M
Volume group
"myvg"
successfully created
[root@Redhat6 ~]
# lvcreate -L 4G -n lv1 myvg #创建LV为4G
Logical volume
"lv1"
created
[root@Redhat6 ~]
# mkfs -t ext4 /dev/myvg/lv1 #格式化LV为ext4
[root@Redhat6 ~]
# blkid #显示设备的UUID及文件系统类型,及卷标
/dev/mapper/vg0-var
: UUID=
"c9776f08-bbaf-4a36-a009-3e16a09ad924"
TYPE=
"ext4"
/dev/sda1
: UUID=
"dc3cc214-a9f6-4730-a186-d08765ccfa4f"
TYPE=
"ext4"
/dev/sda2
: UUID=
"zPpbgE-0Ip7-A4m2-GG4K-sBrC-eUeU-V8VdCI"
TYPE=
"LVM2_member"
/dev/sda5
: UUID=
"e5eLw1-JTrG-H9Q7-18qA-SrPV-axMc-QLPW5M"
TYPE=
"LVM2_member"
/dev/sda6
: UUID=
"7OOZcJ-XzLf-zJJq-JbdF-e386-xCTl-Ym2UE3"
TYPE=
"LVM2_member"
/dev/mapper/vg0-root
: UUID=
"bae7835a-af3b-4935-a04b-5932b2fc123b"
TYPE=
"ext4"
/dev/mapper/vg0-swap
: UUID=
"3e0cb4a7-d393-4f75-af12-1fe6e8c96273"
TYPE=
"swap"
/dev/mapper/vg0-usr
: UUID=
"46d516b8-03ea-4c0d-bb03-0e9d6893bd1a"
TYPE=
"ext4"
/dev/mapper/myvg-lv1
: UUID=
"2d44718c-993d-42e6-896b-05e06af45aee"
TYPE=
"ext4"
[root@Redhat6 ~]
# mkdir /mnt/lv1 #创建LV的挂载点
[root@Redhat6 ~]
# mount /dev/myvg/lv1 /mnt/lv1/ #挂载LV
[root@Redhat6 ~]
# cd /mnt/lv1/ #进入到LV的挂载点
[root@Redhat6 lv1]
# ls
lost+found
[root@Redhat6 lv1]
# cp /etc/rc.sysinit /etc/inittab ./ #copy一个文件到LV的挂载目录里面
[root@Redhat6 lv1]
# ls
inittab lost+found rc.sysinit
[root@Redhat6 lv1]
# lvcreate -L 50M -s -p r -n MY_SNAP /dev/myvg/lv1 #创建快照卷为50M,且只能读,名称为MY_SNAP
Rounding up size to full physical extent 56.00 MiB
Logical volume
"MY_SNAP"
created
[root@Redhat6 lv1]
# mkdir /mnt/snap #创建快照卷的挂载点
[root@Redhat6 lv1]
# mount /dev/myvg/MY_SNAP /mnt/snap/ #挂载快照卷
mount
: block device
/dev/mapper/myvg-MY_SNAP
is write-protected, mounting
read
-only
[root@Redhat6 lv1]
# mkdir /backup #创建备份目录
[root@Redhat6 lv1]
# tar -jcf /backup/lv1.tar.bz2 /mnt/snap/* #把快照卷里面的数据归档
tar
: Removing leading `/' from member names
[root@Redhat6 lv1]
# cp /etc/fstab /mnt/lv1/ #copy文件到LV文件,使LV文件与之前快照的文件有所改变
[root@Redhat6 lv1]
# umount /dev/myvg/MY_SNAP #备份完成后,卸载快照卷的挂载点
[root@Redhat6 lv1]
# lvremove /dev/myvg/MY_SNAP #移除快照卷
Do you really want to remove active logical volume MY_SNAP? [y
/n
]: y
Logical volume
"MY_SNAP"
successfully removed
[root@Redhat6 lv1]
# cd /mnt/lv1/
[root@Redhat6 lv1]
# ls #可以查看到LV文件里面有3个文件
fstab inittab lost+found rc.sysinit
[root@Redhat6 lv1]
# cd /backup/
[root@Redhat6 backup]
# tar xf lv1.tar.bz2 #解压之前备份的文件
[root@Redhat6 backup]
# ls
lv1.
tar
.bz2 mnt
[root@Redhat6 backup]
# cd mnt/lv1/
[root@Redhat6 lv1]
# ls #查看到快照只备份了之前的文件
inittab lost+found rc.sysinit
[root@Redhat6 lv1]
#
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