ASM external redundancy(no mirroring by ASM).

Dear All,

I have a question regarding to oracle ASM External Redundancy technology

For example:

I created an EXTERNAL REDUNDANCY disk group  with 4 disks a year ago.

     CREATE DISKGROUP MYDATA  EXTERNAL REDUNDANCY

     DISK  '/dev/oracleasm/disks/ASM01', '/dev/oracleasm/disks/ASM02','/dev/oracleasm/disks/ASM03', '/dev/oracleasm/disks/ASM04'

Now,  MYDATA keeps very big and important information.

I'm going to remove 2 of the diks('/dev/oracleasm/disks/ASM02','/dev/oracleasm/disks/ASM04') form DISKGROUP MYDATA and add other ones('/dev/oracleasm/disks/ASM05','/dev/oracleasm/disks/ASM06')