一、項目背景描述
1、OSS現網測試數據庫因大量小事物頻繁提交運行非常緩慢。經分析為DS3950存儲所在磁盤I/O存在瓶頸，大量等待事件，性能受限。另外，開發同事沒有優化意識，沒將小事物做成批量提交方式。
2、在DS3950上，9塊600G硬盤(8塊+1塊熱備)做了RAID5陣列，lun01，lun02，lun03，lun04，均為200G，映射給OSS數據庫服務器使用。
3、在操作系統上，lun01，lun02構成了vg_ossdb卷組，vg_ossdb下只有一個LV－－lvoradata掛載在/oradata上。最近因數據增長過快，又將lun03，lun04以vgextend方式擴到了vg_ossdb卷組中去，但尚未擴大lvoradata。
4、在數據庫上，Oracle軟件安裝在本地磁盤/oracle上，數據庫安裝在/oradata上。
二、項目改造計劃及步驟
1、停掉數據庫，將/oradata目錄全備份到另一台備用PC機器上。
2、由於DS3950存儲空閒空很大，可修改其陣列級別從RAID5變為RAID10。
3、由於lun03，lun04尚未使用，領導要求先從vg_ossdb中移除lun03，lun04，並在存儲上unmap掉，便於陣列級別變更。
4、由DBA優化SQL，將小事物盡量做到批量提交方式。
三、系統環境及數據版本說明
[root@ol64 /]# cat /etc/issue
Oracle Linux Server release 6.4
Kernel \r on an \m
[root@ol64 /]# uname -a
Linux ol64.com 2.6.39-400.17.1.el6uek.x86_64 #1 SMP Fri Feb 22 18:16:18 PST 2013 x86_64 x86_64 x86_64 GNU/Linux
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production
PL/SQL Release 11.2.0.4.0 - Production
CORE 11.2.0.4.0 Production
TNS for Linux: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production
四、改造過程中因誤用vgremove將vg_ossdb卷組刪除，而其本意是想用vgreduce移除/dev/sdd，/dev/sde的。
[root@ol64 /]# umount /oradata/ #卸載文件系統
[root@ol64 /]# vgchange -an /dev/vg_ossdb #將卷組置於非激活狀態
0 logical volume(s) in volume group "vg_ossdb" now active
[root@ol64 /]# vgremove vg_ossdb /dev/sdb /dev/sdc /dev/sdd /dev/sde #誤用vgremove命令刪除了vg_ossdb
Do you really want to remove volume group "vg_ossdb" containing 1 logical volumes? [y/n]: y
Do you really want to remove active logical volume lvoradata? [y/n]: y
Logical volume "lvoradata" successfully removed
Volume group "vg_ossdb" successfully removed
Volume group "sdb" not found
Volume group "sdc" not found
Volume group "sdd" not found
Volume group "sde" not found
##################################################################
正確的操作應該是用vgreduce命令從vg_ossdb中移除/dev/sdd和/dev/sde
[root@ol64 /]# vgreduce vg_ossdb /dev/sdd
Removed "/dev/sdd" from volume group "vg_ossdb"
[root@ol64 /]# vgreduce vg_ossdb /dev/sde
Removed "/dev/sde" from volume group "vg_ossdb"
#################################################################
再用pvremove命令移除/dev/sdd和/dev/sde
[root@ol64 ~]# pvremove /dev/sdd
Labels on physical volume "/dev/sdd" successfully wiped
[root@ol64 ~]# pvremove /dev/sde
Labels on physical volume "/dev/sde" successfully wiped
[root@ol64 ~]# pvdisplay #發現/dev/sdb和/dev/sdc所在VG Name為空，冒汗ing.
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_ol64
PV Size 199.51 GiB / not usable 3.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 51074
Free PE 33660
Allocated PE 17414
PV UUID 0dyB8L-p7ZM-Mkcw-76ae-DXPh-U6zg-9kIQ8z
"/dev/sdb" is a new physical volume of "200.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb
VG Name
PV Size 200.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID Ui9wea-II1q-KOx0-96pA-4epf-9hlc-4NFDJF
"/dev/sdc" is a new physical volume of "200.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdc
VG Name
PV Size 200.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID 4VKCJ9-G6kL-QJgg-Titf-UNA8-d3QZ-ZTES3P
[root@ol64 ~]# vgscan #vgscan時找不到vg_ossdb信息，心跳加速，冒汗ing.
Reading all physical volumes. This may take a while...
Found volume group "vg_ol64" using metadata type lvm2
[root@ol64 ~]# lvscan #lvscan時找不到lvoradata信息，大腦一片空白，快要暈倒.
ACTIVE '/dev/vg_ol64/lvopt' [10.01 GiB] inherit
ACTIVE '/dev/vg_ol64/lvroot' [40.01 GiB] inherit
ACTIVE '/dev/vg_ol64/lvswap' [8.00 GiB] inherit
ACTIVE '/dev/vg_ol64/lvhome' [10.01 GiB] inherit
我怎麼會用vgremove命令？？完了！！！vg_ossdb被我誤刪除了。趕緊google和baidu上搜索vg被刪除後如何恢復，可壓根找不到相關資料。冷靜下來後開始思考/etc/lvm/目錄下各文件用途。
更多詳情見請繼續閱讀下一頁的精彩內容： http://www.linuxidc.com/Linux/2013-11/92901p2.htm
