Storage Array Based RAID
If every disk is available through every I/O path, as would be the case if using disk multipathing software, then keep each disk in its own failure group. This is the default Oracle ASM behavior if creating a disk group without explicitly defining failure groups
CREATE DISKGROUP DATA EXTERNAL REDUNDANCY DISK
'/devices/lun1','/devices/lun2','/devices/lun3','/devices/lun4';
For an array with two controllers where every disk is seen through both controllers, create a disk group with each disk in its own failure group
CREATE DISKGROUP DATA NORMAL REDUNDANCY DISK
'/devices/diska1','/devices/diska2','/devices/diska3','/devices/diska4','/devices/diskb1','/devices/diskb2','/devices/diskb3','/devices/diskb4';
Create a disk group with two failure groups, one for each controller, to protect against controller failure
CREATE DISKGROUP DATA NORMAL REDUNDANCY
FAILGROUP controller1 DISK
'/devices/diska1','/devices/diska2','/devices/diska3','/devices/diska4'
FAILGROUP controller2 DISK
'/devices/diskb1','/devices/diskb2','/devices/diskb3','/devices/diskb4';
For a storage network with multiple storage arrays, you want to mirror across storage arrays, then create a disk group with two failure groups, one for each array
CREATE DISKGROUP DATA NORMAL REDUNDANCY
FAILGROUP array1 DISK
'/devices/diska1','/devices/diska2','/devices/diska3','/devices/diska4'
FAILGROUP array2 DISK
'/devices/diskb1','/devices/diskb2','/devices/diskb3','/devices/diskb4';
