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Oracle ASM disk group

An ASM disk group is the fundamental object that ASM manages.
ASM disk groups consist of multiple disks.
ASM disk groups store (ASM) files, possibly from various databases.
The contents of the files are distributed in a way that eliminates hot spots and provides balanced I/O across the disks.

Redundancy levels

A disk group can be created with one of three redundancy levels:
the redundancy level determines the number of tolerated disk failures before the diskgroup is unmounted.

See also

Oracle ASM diskgroup metadata
ASM
Each disk group stores the metadata it needs to manage the space on its disks.

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