Tuesday 9 July 2013

Lesson 60 : Disk Group Redundancy

Disk Group Redundancy

DiskGroup redundancy defines the mirroring level for files stored in the diskgroup. Mirroring protects data integrity by storing copies of data on multiple disks. When you create a disk group, you specify an Oracle ASM disk group type based on one of the following three redundancy levels:

1) Normal for 2-way mirroring

2) High for 3-way mirroring

3) External –No ASM mirroring


The redundancy level controls how many disk failures are tolerated without dismounting the disk group or losing data. Eachmirrored copy is placed on different disks. Hence 2-way mirroring requires minimum of two disks. Similarly, 3-way mirroring requires minimum of three disks assigned to the diskgroup.

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