How many ASM Disk Group(s) do you need, if you want to have the redundancy level set to high
(triple mirroring) for a FILE?
A.
1
B.
2
C.
3
D.
It depends on the number of different disks in a Disk Group, not the number of Disk Groups.
Explanation:
If you want ASM to mirror files, you specify the redundancy level as NORMAL REDUNDANCY (2-way
mirroring by default for most file types) orHIGH REDUNDANCY (3-way mirroring for all files). You
specify EXTERNAL REDUNDANCY if you do not want mirroring by ASM. For example, you might
choose EXTERNAL REDUNDANCY if you want to use storage array protection features.http://docs.oracle.com/cd/B28359_01/server.111/b31107/asmdiskgrps.htm#OSTMG10202
External redundancy
ASM does not provide mirroring redundancy and relies on the storage system to provide RAID functionality. Any write error cause a forced dismount of the disk group. All disks must be located to successfully mount the disk group.
Normal redundancy
ASM provides two-way mirroring. By default all files are mirrored so that there are two copies of every data extent. A loss of one ASM disk is tolerated.
High redundancy
ASM provides triple mirroring by default. A loss of two ASM disks in different failure groups is tolerated.
Failure groups enable the mirroring of metadata and user data. System reliability can diminish if your environment has an insufficient number of failure groups.