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5454
RAID 1 Drive Groups
In RAID 1 drive groups, the RAID controller duplicates all data from one drive to a second drive in the
drive group. A RAID 1 drive group supports an even number of drives from 2 through 32 in a single
span. The RAID1 drive group provides complete data redundancy, but at the cost of doubling the
required data storage capacity. The following table provides an overview of a RAID1 drive group. The
following gure provides a graphic example of a RAID1 drive group.
Uses Use RAID 1 drive groups for small databases or any other environment that
requires fault tolerance but small capacity.
Strong points Provides complete data redundancy.A RAID 1 drive group is ideal for any
application that requires fault tolerance and minimal capacity.
Weak points Requires twice as many drives.
Performance is impaired during drive rebuilds.
Drives 2 through 32 (must be an even number of drives)
Segment 1
RAID 1
Segment 1
Duplicate
Segment 5 Segment 5
Duplicate
...
Segment 2 Segment 2
Duplicate
Segment 6 Segment 6
Duplicate
...
Segment 3
Segment 3
Duplicate
Segment 7 Segment 7
Duplicate
...
Segment 4 Segment 4
Duplicate
Segment 8 Segment 8
Duplicate
...
RAID 1 RAID 1 RAID 1
RAID 5 Drive Groups
A RAID 5 drive group includes disk striping at the block level and parity. Parity is the data’s property of
being odd or even, and parity checking is used to detect errors in the data. In RAID5 drive groups, the
parity information is written to all drives. A RAID5 drive group is best suited for networks that perform
a lot of small input/output (I/O) transactions simultaneously.The following table provides an overview
of a RAID5 drive group. The following gure provides a graphic example of a RAID5 drive group.
Uses Provides high data throughput, especially for large les.
Use RAID 5 drive groups for transaction processing applications because each
drive can read and write independently.
If a drive fails, the RAID controller uses the parity drive to re-create all missing
information.Use also for online customer service that requires fault tolerance.
Use for any application that has high read request rates but random write request
rates.
Strong points Provides data redundancy, high read rates, and good performance in most
environments.Provides redundancy with lowest loss of capacity.
Weak points Not well suited to tasks requiring lots of small writes or small block write
operations.Suffers more impact if no cache is used.
Drive performance is reduced if a drive is being rebuilt.
Environments with few processes do not perform as well because the RAID drive
group overhead is not offset by the performance gains in handling simultaneous
processes.
Drives 3 through 32
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