Storage Administration - Oracle Exadata Recipes: A Problem-Solution Approach - page 244

Normal Redundancy
Listing 9-6 demonstrates what it looks like to create an ASM disk group with normal redundancy.
Listing 9-6. lst09-06-create-diskgroup.sql
SQL> create diskgroup SDATA_CM01
normal redundancy
disk 'o/*/SDATA*'
attribute 'compatible.rdbms' = '11.2.0.3',
'compatible.asm' = '11.2.0.3.0',
'cell.smart_scan_capable' = 'TRUE',
'au_size' = '4M';
Diskgroup created.
SQL>
If we take a look at the raw and usable capacity numbers from V$ASM_DISKGROUP , we can see that the usable
capacity is half the raw capacity of the disk group (see Listing 9-7).
Listing 9-7. lst09-07-asm-normalredundancy.sql
SQL> col name format a12 head 'Disk Group'
SQL> col total_mb format 999999999 head 'Total MB|Raw'
SQL> col free_mb format 999999999 head 'Free MB|Raw'
SQL> col avail_mb format 999999999 head 'Total MB|Usable'
SQL> col usable_mb format 999999999 head 'Free MB|Usable'
SQL> col cdisks format 99999 head 'Cell|Disks'
SQL> select a.name,a.total_mb,a.free_mb,a.type,
decode(a.type,'NORMAL',a.total_mb/2,'HIGH',a.total_mb/3) avail_mb,
decode(a.type,'NORMAL',a.free_mb/2,'HIGH',a.free_mb/3) usable_mb,
count(b.path) cdisks
from v$asm_diskgroup a, v$asm_disk b
where a.group_number=b.group_number
and a.name='SDATA_CM01'
group by a.name,a.total_mb,a.free_mb,a.type,
decode(a.type,'NORMAL',a.total_mb/2,'HIGH',a.total_mb/3) ,
decode(a.type,'NORMAL',a.free_mb/2,'HIGH',a.free_mb/3)
order by 2,1
/
Disk Total MB Free MB Total MB Free MB
Group (Raw) (Raw) Redundancy (Usable) (Usable) # Cell Disks
----------- --------- --------- ---------- ---------- ---------- ------------
SDATA_CM01 5197824 5197320 NORMAL 2598912 2598660 36
SQL>
You can see the disks that make up our newly creating disk group by running the script in Listing 9-8.