內容:(會在後期繼續整理擴充該部分內容;歡迎探討)
1. LVM基本創建及管理
2. LVM快照
3. LVM與RAID的結合使用:基於RAID的LVM
LVM創建:
描述:
LVM是邏輯盤卷管理(LogicalVolumeManager)的簡稱,它是Linux環境下對磁盤分區進行管理的一種機制,LVM是建立在硬盤和分區之上的一個邏輯層,來提高磁盤分區管理的靈活性.
通過創建LVM,我們可以更輕鬆的管理磁盤分區,將若干個不同大小的不同形式的磁盤整合爲一個整塊的卷組,然後在卷組上隨意的創建邏輯卷,既避免了大量不同規格硬盤的管理難題,也使邏輯卷容量的擴充縮減不再受限於磁盤規格;並且LVM的snapshot(快照)功能給數據的物理備份提供了便捷可靠的方式;
創建LVM過程;(如圖)
1. 在物理設備上創建物理分區,每個物理分區稱爲一個PE
2. 使用fdisk工具創建物理分區卷標(修改爲8e),形成PV(Physical Volume 物理卷)
3. 使用vgcreate 將多個PV添加到一個VG(Volume Group 卷組)中,此時VG成爲一個大磁盤;
4. 在VG大磁盤上劃分LV(Logical Volume 邏輯卷),將邏輯卷格式化後即可掛載使用;
各階段可用的命令工具:(詳細選項信息請be a man)
階段 |
顯示信息 |
創建 |
刪除組員 |
擴大大小 |
縮減大小 |
PV |
pvdisplay |
pvcreat |
pvremove |
----- |
----- |
VG |
vgdisplay |
vgcreat |
vgremove |
vgextend |
vgreduce |
LV |
lvdispaly |
lvcreat |
lvremove |
lvextend |
lvreduce |
創建示例:
1. 創建PV
- Device Boot Start End Blocks Id System
- /dev/sdb1 1 609 4891761 8e Linux LVM
- /dev/sdc1 1 609 4891761 8e Linux LVM
- /dev/sdd1 1 609 4891761 8e Linux LVM
- [root@bogon ~]# pvcreate /dev/sd[bcd]1
- Physical volume "/dev/sdb1" successfully created
- Physical volume "/dev/sdc1" successfully created
- Physical volume "/dev/sdd1" successfully created
查看PV信息:
- [root@bogon ~]# pvdisplay
- --- Physical volume ---
- PV Name /dev/sda2
- VG Name vol0
- PV Size 40.00 GB / not usable 2.61 MB
- Allocatable yes
- PE Size (KByte) 32768
- Total PE 1280
- Free PE 281
- Allocated PE 999
- PV UUID GxfWc2-hzKw-tP1E-8cSU-kkqY-z15Z-11Gacd
- "/dev/sdb1" is a new physical volume of "4.67 GB"
- --- NEW Physical volume ---
- PV Name /dev/sdb1
- VG Name
- PV Size 4.67 GB
- Allocatable NO
- PE Size (KByte) 0
- Total PE 0
- Free PE 0
- Allocated PE 0
- PV UUID 1rrc9i-05Om-Wzd6-dM9G-bo08-2oJj-WjRjLg
- "/dev/sdc1" is a new physical volume of "4.67 GB"
- --- NEW Physical volume ---
- PV Name /dev/sdc1
- VG Name
- PV Size 4.67 GB
- Allocatable NO
- PE Size (KByte) 0
- Total PE 0
- Free PE 0
- Allocated PE 0
- PV UUID RCGft6-l7tj-vuBX-bnds-xbLn-PE32-mCSeE8
- "/dev/sdd1" is a new physical volume of "4.67 GB"
- --- NEW Physical volume ---
- PV Name /dev/sdd1
- VG Name
- PV Size 4.67 GB
- Allocatable NO
- PE Size (KByte) 0
- Total PE 0
- Free PE 0
- Allocated PE 0
- PV UUID SLiAAp-43zX-6BC8-wVzP-6vQu-uyYF-ugdWbD
2. 創建VG
- [[root@bogon ~]# vgcreate myvg -s 16M /dev/sd[bcd]1
- Volume group "myvg" successfully created
- ##-s 在創建時指定PE塊的大小,默認是4M。
- 查看系統上VG狀態
- [root@bogon ~]# vgdisplay
- --- Volume group ---
- VG Name myvg
- System ID
- Format lvm2
- Metadata Areas 3
- 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 3
- Act PV 3
- VG Size 13.97 GB ##VG總大小
- PE Size 16.00 MB ##默認的PE塊大小是4M
- Total PE 894 ##總PE塊數
- Alloc PE / Size 0 / 0 ##已經使用的PE塊數目
- Free PE / Size 894 / 13.97 GB ##可用的PE數目及磁盤大小
- VG UUID RJC6Z1-N2Jx-2Zjz-26m6-LLoB-PcWQ-FXx3lV
3. 在VG中劃分出LV:
- [root@bogon ~]# lvcreate -L 256M -n data1 myvg
- Logical volume "data1" created
- ## -L指定LV大小
- ## -n 指定lv卷名稱
- [root@bogon ~]# lvcreate -l 20 -n test myvg
- Logical volume "test" created
- ## -l 指定LV大小佔用多少個PE塊;上面大小爲:20*16M=320M
- [root@bogon ~]# lvdisplay
- --- Logical volume ---
- LV Name /dev/myvg/data
- VG Name myvg
- LV UUID d0SYy1-DQ9T-Sj0R-uPeD-xn0z-raDU-g9lLeK
- LV Write Access read/write
- LV Status available
- # open 0
- LV Size 256.00 MB
- Current LE 16
- Segments 1
- Allocation inherit
- Read ahead sectors auto
- - currently set to 256
- Block device 253:2
- --- Logical volume ---
- LV Name /dev/myvg/test
- VG Name myvg
- LV UUID os4UiH-5QAG-HqOJ-DoNT-mVeT-oYyy-s1xArV
- LV Write Access read/write
- LV Status available
- # open 0
- LV Size 320.00 MB
- Current LE 20
- Segments 1
- Allocation inherit
- Read ahead sectors auto
- - currently set to 256
- Block device 253:3
4. 然後就可以格式化LV,掛載使用:
- [root@bogon ~]# mkfs -t ext3 -b 2048 -L DATA /dev/myvg/data
- [root@bogon ~]# mount /dev/myvg/data /data/
- ## 拷貝進去一些文件,測試後面在線擴展及縮減效果:
- [root@bogon data]# cp /etc/* /data/
5. 擴大LV容量:(2.6kernel+ext3filesystem)
lvextend命令可以增長邏輯卷
resize2fs可以增長filesystem在線或非在線
(我的系統內核2.6.18,ext3文件系統,查man文檔,現在只有2.6的內核+ext3文件系統纔可以在線增容量)
首先邏輯擴展:
- [root@bogon data]# lvextend -L 500M /dev/myvg/data
- Rounding up size to full physical extent 512.00 MB
- Extending logical volume data to 512.00 MB
- Logical volume data successfully resized
- ##-L 500M :指擴展到500M,系統此時會找最近的柱面進行匹配;
- ##-L +500M :值在原有大小的基礎上擴大500M;
- ##-l [+]50 類似上面,但是以Pe塊爲單位進行擴展;
然後文件系統物理擴展:
- [root@bogon data]# resize2fs -p /dev/myvg/data
- resize2fs 1.39 (29-May-2006)
- Filesystem at /dev/myvg/data is mounted on /data; on-line resizing required
- Performing an on-line resize of /dev/myvg/data to 262144 (2k) blocks.
- The filesystem on /dev/myvg/data is now 262144 blocks long.
- ##據上面信息,系統自動識別並進行了在線擴展;
- 查看狀態:
- [root@bogon ~]# lvdisplay
- --- Logical volume ---
- LV Name /dev/myvg/data
- VG Name myvg
- LV UUID d0SYy1-DQ9T-Sj0R-uPeD-xn0z-raDU-g9lLeK
- LV Write Access read/write
- LV Status available
- # open 1
- LV Size 512.00 MB
- Current LE 32
- Segments 1
- Allocation inherit
- Read ahead sectors auto
- - currently set to 256
- Block device 253:2
- ##此時查看掛載目錄,文件應該完好;
6. 縮減LV容量:
縮減容量是一件危險的操作;縮減必須在離線狀態下執行;並且必須先強制檢查文件系統錯誤,防止縮減過程損壞數據;
- [root@bogon ~]# umount /dev/myvg/data
- [root@bogon ~]# e2fsck -f /dev/myvg/data
- e2fsck 1.39 (29-May-2006)
- 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
- DATA: 13/286720 files (7.7% non-contiguous), 23141/573440 blocks
先縮減物理大小:
- [root@bogon ~]# resize2fs /dev/myvg/data 256M
- resize2fs 1.39 (29-May-2006)
- Resizing the filesystem on /dev/myvg/data to 131072 (2k) blocks.
- The filesystem on /dev/myvg/data is now 131072 blocks long.
再縮減邏輯大小:
- [root@bogon ~]# lvreduce -L 256M /dev/myvg/data
- WARNING: Reducing active logical volume to 256.00 MB
- THIS MAY DESTROY YOUR DATA (filesystem etc.)
- Do you really want to reduce data? [y/n]: y
- Reducing logical volume data to 256.00 MB
- Logical volume data successfully resized
查看狀態、重新掛載:
- [root@bogon ~]# lvdisplay
- --- Logical volume ---
- LV Name /dev/myvg/data
- VG Name myvg
- LV UUID d0SYy1-DQ9T-Sj0R-uPeD-xn0z-raDU-g9lLeK
- LV Write Access read/write
- LV Status available
- # open 0
- LV Size 256.00 MB
- Current LE 16
- Segments 1
- Allocation inherit
- Read ahead sectors auto
- - currently set to 256
- Block device 253:2
- 重新掛載:
- [root@bogon ~]# mount /dev/myvg/data /data/
- [root@bogon data]# df /data/
- Filesystem 1K-blocks Used Available Use% Mounted on
- /dev/mapper/myvg-data
- 253900 9508 236528 4% /data
7. 擴展VG,向VG中添加一個PV:
- [root@bogon data]# pvcreate /dev/sdc2
- Physical volume "/dev/sdc2" successfully created
- [root@bogon data]# vgextend myvg /dev/sdc2
- Volume group "myvg" successfully extended
- [root@bogon data]# pvdisplay
- --- Physical volume ---
- PV Name /dev/sdc2
- VG Name myvg
- PV Size 4.67 GB / not usable 9.14 MB
- Allocatable yes
- PE Size (KByte) 16384
- Total PE 298
- Free PE 298
- Allocated PE 0
- PV UUID hrveTu-2JUH-aSgT-GKAJ-VVv2-Hit0-PyoOOr
8. 縮減VG,取出VG中的某個PV:
移除某個PV時,需要先轉移該PV上數據到其他PV,然後再將該PV刪除;
移出指定PV中的數據:
- [root@bogon data]# pvmove /dev/sdc2
- No data to move for myvg
- ##如果sdc2上面有數據,則會花一段時間移動,並且顯示警告信息,再次確認後纔會執行;
- ##如上,提示該分區中沒有數據;
移除PV:
- [root@bogon data]# vgreduce myvg /dev/sdc2
- Removed "/dev/sdc2" from volume group "myvg"
- ##若發現LVM中磁盤工作不太正常,懷疑是某一塊磁盤工作由問題後就可以用該方法移出問題盤
- ##上數據,然後刪掉問題盤;
LVM快照:
描述:
在一個非常繁忙的服務器上,備份大量的數據時,需要停掉大量的服務,否則備份下來的數據極容易出現不一致狀態,而使備份根本不能起效;這時快照就起作用了;
原理:
邏輯卷快照實質是訪問原始數據的另外一個路徑而已;快照保存的是做快照那一刻的數據狀態;做快照以後,任何對原始數據的修改,會在修改前拷貝一份到快照區域,所以通過快照查看到的數據永遠是生成快照那一刻的數據狀態;但是對於快照大小有限制,做快照前需要估算在一定時間內數據修改量大小,如果在創建快照期間數據修改量大於快照大小了,數據會溢出照成快照失效崩潰;
快照不是永久的。如果你卸下LVM或重啓,它們就丟失了,需要重新創建。
創建快照:
- [root@bogon ~]# lvcreate -L 500M -p r -s -n datasnap /dev/myvg/data
- Rounding up size to full physical extent 512.00 MB
- Logical volume "datasnap" created
- ## -L –l 設置大小
- ## -p :permission,設置生成快照的讀寫權限,默認爲RW;r爲只讀
- ##-s 指定lvcreate生成的是一個快照
- ##-n 指定快照名稱
- 掛載快照到指定位置:
- [root@bogon ~]# mount /dev/myvg/datasnap /backup/
- mount: block device /dev/myvg/datasnap is write-protected, mounting read-only
- 然後備份出快照中文件即可,備份後及時刪除快照:
- [root@bogon ~]# ls /backup/
- inittab lost+found
基於RAID的LVM的建立:
描述:
基於RAID的LVM,可以在底層實現RAID對數據的冗餘或是提高讀寫性能的基礎上,可以在上層實現LVM的可以靈活管理磁盤的功能;
如圖:
建立過程:
1. 建立LinuxRAID形式的分區:
- Device Boot Start End Blocks Id System
- /dev/sdb1 1 62 497983+ fd Linux raid autodetect
- /dev/sdc1 1 62 497983+ fd Linux raid autodetect
- /dev/sdd1 1 62 497983+ fd Linux raid autodetect
- /dev/sde1 1 62 497983+ fd Linux raid autodetect
2. 創建RAID-5:
- [root@nod1 ~]# mdadm -C /dev/md0 -a yes -l 5 -n 3 -x 1 /dev/sd{b,c,d,e}1
- mdadm: array /dev/md0 started.
- # RAID-5有一個spare盤,三個活動盤。
- # 查看狀態,發現跟創建要求一致,且創建正在進行中:
- [root@nod1 ~]# cat /proc/mdstat
- Personalities : [raid6] [raid5] [raid4]
- md0 : active raid5 sdd1[4] sde1[3](S) sdc1[1] sdb1[0]
- 995712 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
- [=======>.............] recovery = 36.9% (184580/497856) finish=0.2min speed=18458K/sec
- unused devices: <none>
- # 查看RAID詳細信息:
- [root@nod1 ~]# mdadm -D /dev/md0
- /dev/md0:
- Version : 0.90
- Creation Time : Wed Apr 6 04:27:46 2011
- Raid Level : raid5
- Array Size : 995712 (972.54 MiB 1019.61 MB)
- Used Dev Size : 497856 (486.27 MiB 509.80 MB)
- Raid Devices : 3
- Total Devices : 4
- Preferred Minor : 0
- Persistence : Superblock is persistent
- Update Time : Wed Apr 6 04:36:08 2011
- State : clean
- Active Devices : 3
- Working Devices : 4
- Failed Devices : 0
- Spare Devices : 1
- Layout : left-symmetric
- Chunk Size : 64K
- UUID : 5663fc8e:68f539ee:3a4040d6:ccdac92a
- Events : 0.4
- Number Major Minor RaidDevice State
- 0 8 17 0 active sync /dev/sdb1
- 1 8 33 1 active sync /dev/sdc1
- 2 8 49 2 active sync /dev/sdd1
- 3 8 65 - spare /dev/sde1
3. 建立RAID配置文件:
- [root@nod1 ~]# mdadm -Ds > /etc/mdadm.conf
- [root@nod1 ~]# cat /etc/mdadm.conf
- ARRAY /dev/md0 level=raid5 num-devices=3 metadata=0.90 spares=1 UUID=5663fc8e:68f539ee:3a4040d6:ccdac92a
4. 基於剛建立的RAID設備創建LVM:
- # 將md0創建成爲PV(物理卷):
- [root@nod1 ~]# pvcreate /dev/md0
- Physical volume "/dev/md0" successfully created
- # 查看物理卷:
- [root@nod1 ~]# pvdisplay
- "/dev/md0" is a new physical volume of "972.38 MB"
- --- NEW Physical volume ---
- PV Name /dev/md0
- VG Name #此時該PV不包含在任何VG中,故爲空;
- PV Size 972.38 MB
- Allocatable NO
- PE Size (KByte) 0
- Total PE 0
- Free PE 0
- Allocated PE 0
- PV UUID PUb3uj-ObES-TXsM-2oMS-exps-LPXP-jD218u
- # 創建VG
- [root@nod1 ~]# vgcreate myvg -s 32M /dev/md0
- Volume group "myvg" successfully created
- # 查看VG狀態:
- [root@nod1 ~]# vgdisplay
- --- Volume group ---
- VG Name myvg
- System ID
- Format lvm2
- Metadata Areas 1
- 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 1
- Act PV 1
- VG Size 960.00 MB
- PE Size 32.00 MB
- Total PE 30
- Alloc PE / Size 0 / 0
- Free PE / Size 30 / 960.00 MB
- VG UUID 9NKEWK-7jrv-zC2x-59xg-10Ai-qA1L-cfHXDj
- # 創建LV:
- [root@nod1 ~]# lvcreate -L 500M -n mydata myvg
- Rounding up size to full physical extent 512.00 MB
- Logical volume "mydata" created
- # 查看LV狀態:
- [root@nod1 ~]# lvdisplay
- --- Logical volume ---
- LV Name /dev/myvg/mydata
- VG Name myvg
- LV UUID KQQUJq-FU2C-E7lI-QJUp-xeVd-3OpA-TMgI1D
- LV Write Access read/write
- LV Status available
- # open 0
- LV Size 512.00 MB
- Current LE 16
- Segments 1
- Allocation inherit
- Read ahead sectors auto
- - currently set to 512
- Block device 253:2
問題:(實驗環境,很難做出判斷,望有經驗的多做指教)
在RAID上實現LVM後,不能再手動控制陣列的停止。
raid設備在建成以後,是不可以改變活動磁盤數目的。只能新增備份盤, 刪除故障盤。故,若對存儲需求估計失誤,raid上層的LVM分區即使可以擴展, 但是仍可能無法滿足存儲需求;
如果整個raid不能滿足容量需求,在試驗中是可以實現將兩個RAID同時加入 一個VG,從而實現RAID間的無縫銜接~但是這樣做在實際生產中效果怎麼樣?是 否會因爲架構太複雜造成系統負過大,或是對拖慢I/O響應速度?!這仍舊是個問 題;
基於RAID之上的LVM,若劃分多個LV,多個LV之間的數據分佈情況怎麼樣?! 會不會拖慢RAID本來帶來的性能提升?
RAID間的無縫銜接示意圖: