ASM SAN migration Case Study:

Problem:
I need to remove 3 old SAN disks(size of 150 G each) from my ASM database without any down time.

Server, OS and DB details:
OS: RHEL 4 Update 4 (64 bit)
DB: 10.2.0.3.0
Server: DELL PowerEdgeTM 2950(16G Memory, 4 CPU's(Intel(R) Xeon(R) CPU 5160 @ 3.00GHz))


Procedure:
1. Make sure you have free disks available to add to the ASM diskgroup, before dropping the disk's:

On ASM instance:
sqlplus / as sysdba

set linesize 200;
col path format a20;

select NAME, PATH, MOUNT_STATUS, HEADER_STATUS, MODE_STATUS, TOTAL_MB, FREE_MB
from v$asm_disk;


2. Add new ASM disks to the diskgroup:

alter diskgroup ORADB_DATA01_DG add disk 'ORCL:H_1253_1521';
alter diskgroup ORADB_DATA01_DG add disk 'ORCL:H_1253_1522';
alter diskgroup ORADB_DATA01_DG add disk 'ORCL:H_1253_1523';

alter diskgroup ORADB_DATA01_DG REBALANCE POWER 10; or
alter system set asm_power_limit=10 scope=memory;

-- Check the rebalance operation
select * from v$asm_operation;


Time taken to rebalance the diskgroup: app. 90 min.


3. Identify the disks to drop from the diskgroup:

set linesize 200;
col path format a20;

select NAME, PATH, MOUNT_STATUS, HEADER_STATUS, MODE_STATUS, TOTAL_MB, FREE_MB
from v$asm_disk;

ALTER DISKGROUP ORADB_DATA01_DG DROP DISK B_1530_1091;
ALTER DISKGROUP ORADB_DATA01_DG DROP DISK C_1530_1090;
ALTER DISKGROUP ORADB_DATA01_DG DROP DISK D_1530_1081;

alter diskgroup ORADB_DATA01_DG REBALANCE POWER 10; or
alter system set asm_power_limit=10 scope=memory;

-- Check the rebalance operation
select * from v$asm_operation;


Time taken to rebalance the diskgroup: app. 90 min.


4. Physically removing the disks from the server:

as root only!!!

/etc/init.d/oracleasm deletedisk B_1530_1091
/etc/init.d/oracleasm deletedisk C_1530_1090
/etc/init.d/oracleasm deletedisk D_1530_1081


How to find mapping of ASM disks to Physical Devices?

a.
atlxd215 | +ASM | /dev
> /etc/init.d/oracleasm querydisk H_1253_1521
Disk "H_1253_1521" is a valid ASM disk on device [120, 113]

b.
atlxd215 | +ASM | /dev
> ls -l /dev | grep 120 | grep 113
brwxrwx--- 1 oracle dba 120, 113 Oct 1 10:55 emcpowerh1

[or]

atlxd215 | +ASM | /dev
> cd oracleasm
atlxd215 | +ASM | /dev/oracleasm
> cd disks

atlxd215 | +ASM | /dev/oracleasm/disks
> ls -lt
total 0
brw-rw---- 1 oracle dba 120, 177 Oct 1 11:04 L_1253_1561
brw-rw---- 1 oracle dba 120, 161 Oct 1 11:04 K_1253_1560
brw-rw---- 1 oracle dba 120, 145 Oct 1 11:04 J_1253_1541
brw-rw---- 1 oracle dba 120, 129 Oct 1 11:03 I_1253_1540
brw-rw---- 1 oracle dba 120, 113 Oct 1 11:03 H_1253_1521
brw-rw---- 1 oracle dba 120, 97 Oct 1 11:03 G_1253_1520
brw-rw---- 1 oracle dba 120, 81 Oct 1 11:03 F_1253_1501
brw-rw---- 1 oracle dba 120, 65 Oct 1 10:59 E_1253_1500

c.
If you are using multi-path, you will need an additional step to map the physical device to the multi-path device:

as root only!!!

# /sbin/powermt display dev=emcpowerh1