ASM provides ???Striping and Mirroring Everything??? (SAME) for many types of disks,
including ???Just a Bunch of Disks??? (JBOD) arrays. You can specify groups of disks,
and designate a failure group to be used in the result of a disk failure. Mirroring can
also be set up on a per-file basis, and you can specify one or two mirrors. ASM
includes the ability to detect disk ???hot spots??? and redistribute data to avoid disk
bottlenecks, as well as the capability of adding disks to a disk group without any
interruption in service. DBAs add the disks to disk groups or remove disks from disk
groups using Oracle Enterprise Manager.
Figure 11-3. RAID levels commonly used with an Oracle database
DATA DATA
DATA DATA DATA DATA
D
PARITY
C
B
PARITY
A
D
C
A
B
PARITY
D
C
D
B
A
B
C
A
PARITY
RAID-O: Simple Striping, No Redundancy
RAID-1: Simple Mirroring
RAID-0+1: Striping and Mirroring
RAID-5: Striping with Distributed Parity
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266 | Chapter 11: Oracle and High Availability
Stored data is automatically rebalanced when disks are added or removed.
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