向已有的ASM 磁盘组增加磁盘的方法:

1. 加硬盘,分区,用fdisk -l 查看分区表
2. 在root用户下
/etc/init.d/oracleasm listdisks
/etc/init.d/oracleasm createdisk VOL4 /dev/sde1

然后到另一节点
/etc/init.d/oracleasm scandisks

3.到oracle下
export ORACLE_SID=+ASM1
sqlplus / as sysdba
select state,header_status,substr(name,1,12) Name,free_mb,
substr(path,1,16) PATH from v$asm_disk;
STATE HEADER_STATUS NAME FREE_MB PATH
---------------- ------------------------ ------------------------ ---------- --------------------------------
NORMAL PROVISIONED 0 ORCL:VOL4
NORMAL PROVISIONED 0 ORCL:VOL5
NORMAL PROVISIONED 0 ORCL:VOL6
NORMAL MEMBER VOL1 1089 ORCL:VOL1
NORMAL MEMBER VOL2 1090 ORCL:VOL2
NORMAL MEMBER VOL3 1601 ORCL:VOL3

查看是否已经找到硬盘.状态为PROVISIONED为新增的硬盘.

然后
show parameter asm_diskgroups;
alter diskgroup dg1 add disk 'ORCL:VOL4';
这样就加入了新的硬盘,再次查询
select state,header_status,substr(name,1,12) Name,free_mb,
substr(path,1,16) PATH from v$asm_disk;
观察是否已经加入硬盘
STATE HEADER_STATUS NAME FREE_MB PATH
---------------- ------------------------ ------------------------ ---------- --------------------------------
NORMAL PROVISIONED 0 ORCL:VOL5
NORMAL PROVISIONED 0 ORCL:VOL6
NORMAL MEMBER VOL1 1089 ORCL:VOL1
NORMAL MEMBER VOL2 1090 ORCL:VOL2
NORMAL MEMBER VOL3 1601 ORCL:VOL3
NORMAL MEMBER VOL4 1091 ORCL:VOL4

4.删除ASM磁盘.
alter diskgroup dgroup1 drop disk VOL4;

5.增加或删除磁盘后.一般会自动平衡磁盘.
init.ora参数asm_power_limit用于影响重新平衡操作的吞吐量和速度。asm _power_limit的取值范围是0到11，值为11表示全速，而值为0表示低速。
用户应该谨慎使用值0，这会关闭自动重新平衡。

6.手工平衡.
ALTER DISKGROUP DG1 REBALANCE;
select group_number,name,total_mb,free_mb from v$asm_disk_stat;
使diskgroup mount
alter diskgroup DG1 mount;
show parameter asm_diskgroups
如果要卸载diskgroup，使用下面的命令：
ALTER DISKGROUP ALL DISMOUNT;