A database instance is using an Automatic Storage Management (ASM) instance, which has a disk group, DGROUP1, created as follows:
SQL> CREATE DISKGROUP dgroup1 NORMAL REDUNDANCY
FAILGROUP controller1 DISK '/devices/diska1', '/devices/diska2' FAILGROUP controller2 DISK
'/devices/diskb1', '/devices/diskb2' ;
What happens when the whole CONTROLLER1 Failure group is damaged?
A. The transactions that use the disk group will halt.
B. The mirroring of allocation units occurs within the CONTROLLER2 failure group.
C. The data in the CONTROLLER1 failure group is shifted to the CONTROLLER2 failure group and implicit rebalancing is triggered.
D. The ASM does not mirror any data and newly allocated primary allocation units (AU) are stored in the CONTROLLER2 failure group.
可以看到创建的磁盘组冗余度是 normal。当一个磁盘组故障时，磁盘首先离线，然后自动的被 drop，到那时磁盘组仍然挂载和服务的，由于有镜像，所以磁盘组中的数据都是可访问的，ASM 会自动的在故障盘上执行再平衡，使用冗余数据重建,C 对。
事务不会停止，数据会从镜像磁盘组中读取，A 错。 controller2 故障组是镜像磁盘组，不会发生分配单元，会将 controller1 数据镜像到 controller2，B,D 错，因为并未增加磁盘，AU 大小也没变化，故不会分配新的 AU。