For each device (sda to sdu) enter:

$ fdisk /dev/sda
Command (m for help): u
Command (m for help): p
Command (m for help): n
Command (m for help): p
1
32768
 
 w

(Where ?? are the characters used to identify the device.)
The reason we are using 32768 as the start block for the device is because of the way scsi/san volume mapping uses the first few blocks of a device and subsequently causes excessive write I/O. This is better explained in the following link:
http://www.pythian.com/news/411/aligning-asm-disks-on-linux

e.g.
# fdisk /dev/sda
Command (m for help): u
Changing display/entry units to sectors
Command (m for help): p
Disk /dev/sda: 5394 MB, 5394923520 bytes
166 heads, 62 sectors/track, 1023 cylinders, total 10536960 sectors
Units = sectors of 1 * 512 = 512 bytes
   Device Boot      Start         End      Blocks   Id  System
Command (m for help): n
Command action
   e   extended
   p   primary partition (1-4)
p
Partition number (1-4): 1
First sector (62-10536959, default 62): 32768
Last sector or +size or +sizeM or +sizeK (32768-10536959, default 10536959):
Using default value 10536959
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
#

Reboot the system

The command “cat /proc/partitions” (should now list extra sd partitions)

e.g.
cat /proc/partitions
major minor  #blocks  name

104       0   71652960 cciss/c0d0
104       1       104391 cciss/c0d0p1
104       2   71545477 cciss/c0d0p2
    8       0     5268480 sda
    8       1     5252096 sda1
    8     16     5268480 sdb
    8     17     5252096 sdb1
    8     32     5268480 sdc
    8     33     5252096 sdc1
    8     48     5268480 sdd
    8     49     5252096 sdd1
    8     64     5268480 sde
    8     65     5252096 sde1
    8     80     5268480 sdf
    8     81     5252096 sdf1
    8     96     5268480 sdg
    8     97     5252096 sdg1
    8   112     5268480 sdh
    8   113     5252096 sdh1
    8   128     5268480 sdi
    8   129     5252096 sdi1
    8   144     5268480 sdj
    8   145     5252096 sdj1
    8   160     5268480 sdk
    8   161     5252096 sdk1
    8   176     5268480 sdl
    8   177     5252096 sdl1
Etc

# ls /dev/sd*
/dev/sda   /dev/sdah  /dev/sdb   /dev/sdf1  /dev/sdk   /dev/sdo1 /dev/sdt    /dev/sda1 /dev/sdai  /dev/sdb1 
/dev/sdg   /dev/sdk1  /dev/sdp   /dev/sdt1  /dev/sdaa /dev/sdaj  /dev/sdc    /dev/sdg1 /dev/sdl    /dev/sdp1 
/dev/sdu   /dev/sdab  /dev/sdak /dev/sdc1 /dev/sdh   /dev/sdl1  /dev/sdq    /dev/sdu1 /dev/sdac /dev/sdal 
/dev/sdd   /dev/sdh1  /dev/sdm  /dev/sdq1 /dev/sdv   /dev/sdad /dev/sdam /dev/sdd1 /dev/sdi    /dev/sdm1 

# ls /dev/mapper/
ASM1        ASM13      ASM16p1  ASM4p1   ASM8      OCR2                            VOTE2
ASM10      ASM13p1  ASM1p1    ASM5       ASM8p1  OCR2p1                        VOTE2p1
ASM10p1  ASM14      ASM2        ASM5p1   ASM9      VolGroup00-LogVol00   VOTE3

# ls /dev/mpath
ASM1        ASM12      ASM14p1  ASM1p1  ASM4      ASM6p1  ASM9      OCR2p1    VOTE3
ASM10      ASM12p1  ASM15      ASM2      ASM4p1  ASM7      ASM9p1  VOTE1      VOTE3p1
ASM10p1  ASM13      ASM15p1  ASM2p1  ASM5      ASM7p1  OCR1      VOTE1p1

edit /etc/sysconfig/oracleasm

ORACLEASM_SCANORDER=”sd”
ORACLEASM_SCANEXCLUDE=”dm”

Copy this file to each of the cluster nodes.