What happens if the CONTROLLER1 failure group becomes unavailable due to error of for maintenance?

B.
Mirroring of allocation units will be done to ASM disks in the CONTROLLER2 failure group until the CONTROLLER1 for failure group is brought back online.

B

B or D? B looks ok!!!

B TRUE
Because we still have two disks in controller2, ASM will try to mirrow until there’s space.

http://docs.oracle.com/cd/E11882_01/server.112/e18951/asmdiskgrps.htm#OSTMG94124

From note Doc ID 466326.1
Oracle Database 11g introduces the ASM Fast Mirror Resync feature that significantly reduces the time required to resynchronize a transient failure of a disk. When a disk goes off line oracle engine doesn’t balance other disk, instead ASM tracks the allocation units that are modified during the outage. The content present in the failed disk is tracked by other disks and any modification that is made to the content of failed disk is actually made in other available disks. Once we get the disk back and attach it, the data belonging to this disk and which got modified during that time will get resynchronized back again. This avoids the heavy re-balancing activity.

B is wrong…

It’s D

Doc ID 946213.1

If the ASM diskgroup is created with two failure groups, the loss of one entire failure group is tolerated with no downtime.

The diskgroup continues to operate normally, allocating space in the one surviving failure group. The failed disks show up in V$ASM_DISK twice (as of 10.1.0.4): once as missing and candidate statuses for HEADER_STATUS and STATE, respectively, and another as offline hung. The reason that you have missing, candidate, and offline hung disks is that you have had a failure group crash, and an insufficient number of surviving failure groups exists to complete a rebalance successfully to restore the contents from the failed disks. The offline hung entries in V$ASM_DISK essentially track the fact that there are extents whose redundancy has not yet been restored.

To restore the disks to a normal status, you need to add back the missing disks. To add the disks back, you must specify the FORCE flag, as in the following example, because they still have their old disk headers:

SQL> ALTER DISKGROUP DATA ADD FAILGROUP SAN2 DISK
‘/dev/rdsk/c3t19d3s4′ FORCE,’/dev/rdsk/c3t19d4s4’ FORCE,
‘/dev/rdsk/c3t19d5s4’ FORCE, ‘/dev/rdsk/c3t19d6s4’ FORCE REBALANCE POWER ;

When adding back the disks, be sure to specify the previously used failure group name. Adding these disks initiates a rebalance. Once the rebalance completes from adding back the disks from the failed failure group, the offline hung entries should go away.