617.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.
Answer: C
答案解析：
参考：http://blog.csdn.net/rlhua/article/details/12972983
标准冗余，ASM要求该磁盘组至少要拥有两个failure磁盘组，即提供双倍镜像保护，对于同一份数据(ASM中镜像单位不是磁盘，也不是块，而是一种AU的单位，该单位大小默认是1M)将有主从两份镜像，并且ASM通过算法来自动确保主、从镜像不会存在于同一份failure 磁盘组，这样就保障了就算整个failure 磁盘组都损坏，数据也不会丢失。
该题中创建磁盘组使用了NORMAL REDUNDANCY即是说，该磁盘组拥有两个或两个以上的磁盘组成一组故障磁盘组，提供双倍镜像保护，题中为两个磁盘。
controller1组中包含两个磁盘， '/devices/diska1', '/devices/diska2'
controller2 组中包含两个磁盘，'/devices/diskb1', '/devices/diskb2' ;
如果controller1被破坏，则数据就会转移到controller2 ，并且自动rebalance。