HOW TO ADD ASM DISK in AIX 

There is not required that all the disks have the same name across all the nodes. This just makes easier the administration when having large number of disks. What is relevant for ASM, is that all the disks can be discovered (asm_diskstring). When the disk is validated in the other nodes, ASM reads the header of the disk in order to complete the operation. The disks are discovered based on the asm_diskstring parameter.

There are default paths for the platforms and those directories will be scanned even if parameter asm_diskstring is not set. The devices with right permissions will be discovered.

Some of the common causes that cause the disk not been discovered are:

* If using ASMLIB, the command /etc/init.d/oracleasm scandisk was not executed in the remaining nodes of the
cluster.
* Incorrect permissions. Oracle user is not the owner or can not read/write.
* The disk is not present under any name.
* In Linux when using raw bindings and the raw name is consistent across the nodes, either the device
is incorrect (different disk), or there are missing entries in file /proc/partitions.
* The name could be the same across all the nodes, but they are not pointing to the same device.
* In IBM AIX, when using disks without LVM, there are particular attributes for the disks (Table 1).

STORAGE TYPE
ATTRIBUTE
VALUE
IBM STORAGE (ESS,FasTt,DSXXX) reserve_policy no_reserve
EMC STORAGE reserve_lock no
Table 1
For example, using ESS disks and configuring them with reserve_policy=single_path, will allow to mount the diskgroup only in one node. As an additional test, dd command can be used to read from the device on the second node. A failure of this operation at the Operating System level, demonstrate the cause is related to the disk configuration.

lsattr -E -l hdisk19|grep reser
reserve_policy no_reserve Reserve Policy True
lsattr -E -l hdisk21|grep reser
reserve_policy single_path Reserve Policy True
*********** Wont be discovered in a second node

Have this note handy: ORA-15040, ORA-15066, ORA-15042 when ASM disk is not present in all nodes of a Rac Cluster. Adding a disk to the Diskgroup fails. ( Doc ID 399500.1 )


Add New Disk to RAC ASM Instance:

1. Adding new LUN to Servers

2. Both LUN (hdisk) name should be same on both the nodes

3. Check for the reserve_policy status, It should be no_reserv

lsattr -R -l hdisk15|grep reser

chdev -l hdisk15 -a reserve_policy=no_reserve

4. Change the ownership to grid user

chown grid:oinstall /dev/hdisk15
chown grid:oinstall /dev/rhdisk15

5. Change the permission to 660 for all the hdisk
chmod 660 /dev/rhdisk15
chmod 660 /dev/hdisk15
6. Then check the asm_disk for visibility of the new disk

7. ALTER DISKGROUP DATA ADD DISK '/dev/rhdisk15' NAME DATA_0002 SIZE 307200 M REBALANCE POWER 11;