Oracle Installer can’t discover ASM disks Ora-15186 Asmlib Error =[ASM_OPEN], ERROR = [1]

I could get ASM commandline to discover ASM disks at both RAC nodes. It can map VOL1, VOL2 at both nodes but Oracle RAC database installer won’t see ASM disks.

Operating System Linux Red Hat Advanced Server OS Version 4.0 Update Version Nahant Update 3
On WYGORA01
[root@wygora01 software]# /etc/init.d/oracleasm createdisk VOL1 /dev/mapper/mpath5
Marking disk “/dev/mapper/mpath5” as an ASM disk: [ OK ]
[root@wygora01 software]# /etc/init.d/oracleasm createdisk VOL1 /dev/mapper/mpath6
root@wygora01 software]# /etc/init.d/oracleasm createdisk VOL2 /dev/mapper/mpath6
Marking disk “/dev/mapper/mpath6” as an ASM disk: [ OK ]
On WYGORA02
[root@wygora02 ~]# /etc/init.d/oracleasm scandisks
Scanning system for ASM disks: [ OK ]

[root@wygora02 ~]# /etc/init.d/oracleasm listdisks
VOL1
VOL2
[root@wygora01 ~]# /etc/init.d/oracleasm listdisks
VOL1
VOL2
Initially I was trying to get oracle installer to create ASM instance. Somehow installer couldn’t list VOL1 & VOL2 disks though ASM listdisk could see it. After carrying ASM dropdisk/createdisk fixed it but restart was causing same issue. I decided to go ahead with installation and see if Oracle builds an environment . Installer managed to start ASM1 instance but failed to build ASM2 instance on another RAC node.

I tried starting the ASM2 instance manually and came across error

SQL> startup pfile=/u01/app/oracle/product/10.2.0/asm/admin/+ASM/pfile/init.ora
ASM instance started
Total System Global Area 130023424 bytes
Fixed Size 2019032 bytes
Variable Size 102838568 bytes
ASM Cache 25165824 bytes
ORA-15032: not all alterations performed
ORA-15063: ASM discovered an insufficient number of disks for diskgroup “DATA”
SQL> select PATH, MOUNT_STATUS, HEADER_STATUS, MODE_STATUS, STATE from V$ASM_DISK;
no rows selected
SQL> alter diskgroup all mount;
alter diskgroup all mount
*
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15063: ASM discovered an insufficient number of disks for diskgroup “DATA”

Reason behind Error

Multipath storage devices were accessed by different paths on both nodes.

Solution : Add asm_diskstring = ‘/dev/oracleasm/disks/*’ at ASM init.ora file & bounce the box