Using Raw Devices in Oracle ASM-Fighting

奥尔覅几22

　　Q:When will you use raw devices in ASM?
　　A:
　　1.There's no approximate asmlib for kernel of your host
　　2.You wanna promote I/O performance of database under your estimation compared with FS
　　How to create raw devices in linux?
　　Environment:Redhat 5.4|Oracle Grid Infrastucture+Oracle Database 11G r2
　　That's an example:
　　1.Add two disks to current system:/dev/sdg    /dev/sdh
　　2.Create 2 partitions every disk:/dev/sdg1  /dev/sdg2     /dev/sdh1   /dev/sdh2
　　If you run asmca with grid user,you cannot find any available disk
　　3.Create raw devices
vim /etc/udev/rules.d/60-raw.rules　　
ACTION=="add",KERNEL=="/dev/sdg1",RUN+="/bin/raw /dev/raw/raw1 %N"
　　
ACTION=="add",KERNEL=="/dev/sdg2",RUN+="/bin/raw /dev/raw/raw2 %N"
　　
ACTION=="add",KERNEL=="/dev/sdh1",RUN+="/bin/raw /dev/raw/raw3 %N"
　　
ACTION=="add",KERNEL=="/dev/sdh2",RUN+="/bin/raw /dev/raw/raw4 %N"
　　
KERNEL=="raw?",OWNER="grid" GROUP="oinstall",MODE="0660"
　　
start_udev
　　4.Create ASM diskgroup
su - grid　　
sqlplus / as sysasm
　　
alter system set disk_strings='/dev/raw/raw1,/dev/raw/raw2,/dev/raw/raw3,/dev/raw/raw4' scope=spfile;
　　
startup force;
　　
CREATE DISKGROUP TESTDG1 NORMAL REDUNDANCY
　　FAILGROUP FG1
　　DISK '/dev/raw/raw1' NAME F1_D1
　　DISK '/dev/raw/raw3' NAME F1_D2
　　FAILGROUP FG2
　　DISK '/dev/raw/raw2' NAME F2_D1
　　DISK '/dev/raw/raw4' NAME F2_D2;