Create ASM Disk on RHEL5 or OEL5
Ok, this is just my simple note about how to create ASM disk 
Assumption: Disk already partitioned and oracleasm package has been installed.
If not, partition it using fdisk and download oracleasm package from here
Firstly, configure the Oracle Linux ASMLib driver
# oracleasm configure -i
Configuring the Oracle ASM library driver.
This will configure the on-boot properties of the Oracle ASM library
driver. The following questions will determine whether the driver is
loaded on boot and what permissions it will have. The current values
will be shown in brackets ('[]'). Hitting <ENTER> without typing an
answer will keep that current value. Ctrl-C will abort.
Default user to own the driver interface []: oracle
Default group to own the driver interface []: dba
Start Oracle ASM library driver on boot (y/n) [n]: y
Scan for Oracle ASM disks on boot (y/n) [y]: y
Writing Oracle ASM library driver configuration: done
Then, load and initialize the ASMLib driver
# oracleasm init
Creating /dev/oracleasm mount point: /dev/oracleasm
Loading module "oracleasm": oracleasm
Mounting ASMlib driver filesystem: /dev/oracleasm
Then, create the asm disk laaa..
# oracleasm createdisk ASMDISK01 /dev/sdc1
Writing disk header: done
Instantiating disk: done
# oracleasm createdisk ASMDISK02 /dev/sdd1
Writing disk header: done
Instantiating disk: done
# oracleasm createdisk ASMDISK03 /dev/sde1
Writing disk header: done
Instantiating disk: done
and so on..
Then, Scan the system for Oracle ASMLib disks
# oracleasm scandisks
Reloading disk partitions: done
Cleaning any stale ASM disks...
Scanning system for ASM disks...
Finally, list known Oracle ASMLib disks to check either the disk created or not
# oracleasm listdisks
ASMDISK01
ASMDISK02
ASMDISK03
ASMDISK04
ASMDISK05
ASMDISK06
ASMDISK07
ASMDISK08
ASMDISK09
ASMDISK10
ASMDISK11
ASMDISK12
ASMDISK13
If everything ok, then done..
p/s: ASMDISK# can be any name such as MYDISK#, YOURDISK# etc.
