While installation of 11gR2, ASM disk was not visible.
permission were not given on ASMDISKS.
ls -lart /dev/sd*
brw-r----- 1 root disk 8, 17 Apr 1 12:53 sdb1
brw-r----- 1 root disk 8, 49 Apr 1 12:53 sdd1
brw-r----- 1 root disk 8, 65 Apr 1 12:53 sde1
brw-r----- 1 root disk 8, 81 Apr 1 12:53 sdf1
brw-r----- 1 root disk 8, 97 Apr 1 12:53 sdg1
Later on I remind myself that I forget to add below lines in /etc/rc.d/rc.local
chown oracle:dba /dev/sdb1
chown oracle:dba /dev/sdc1
chown oracle:dba /dev/sdd1
chown oracle:dba /dev/sde1
chown oracle:dba /dev/sdf1
chown oracle:dba /dev/sdg1
chmod 660 /dev/sdb1
chmod 660 /dev/sdc1
chmod 660 /dev/sdd1
chmod 660 /dev/sde1
chmod 660 /dev/sdf1
chmod 660 /dev/sdg1
Define the Scanorder in /etc/sysconfig/oracleasm config file. For example, if the used multipathing device is /dev/md1, you have to force the ASMlib to scan the /dev/md* paths before the /dev/sd* paths
vi /etc/sysconfig/oracleasm
ORACLEASM_SCANORDER: Matching patterns to order disk scanning
ORACLEASM_SCANORDER="md sd"
