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RAID 3
Block Striping with Dedicated Parity - Data is broken into logical blocks, the size of
a SCSI disk block, and striped across several drives. One drive is dedicated to
parity. In the event of failure, original data is re-generated from the parity informa-
tion.
Drive 0
Drive 1
A0
A1
A4
B0
B3
B4
C2
C3
RAID 5
Multiple Block Striping with Dedicated Parity - Sets a given number logical blocks
as a unit for striping across several drives. For small read/write, as few as one drive
may be activated for improved small record access speed. Parity information is
interleaved across the drive array. In the event of failure, original data is regener-
ated from the parity information.
Drive 0
Drive 1
A0-A1
A2-A3
B3-B4
P
D1-D2
D3-D4
E4-F0
F1-F2
Required Number of Drives and Net Capacity
Following is a summary of the minimum number of drives required and the capacity
available for the different types of RAID operation:
OPERATION
RAID 0
RAID 1
RAID 0 + 1
RAID 3
RAID 5
T = Sum of the capacity of all connected drives
n = Number of connected drives
18
C. RAID Concept
Drive 2
Drive 3
A2
A3
B1
B2
C0
C1
C4
D0
Drive 2
Drive 3
A4-B0
B1-B2
C0-C1
C2-C3
P
E0-E1
F3-F4
P
MIN. DRIVES
2
2
4
3
3
ASUS PCI-DA2100 User's Manual
Drive 4
P
P
P
P
Drive 4
P
C4-D0
E2-E3
G0-G1
CAP. AVAILABLE
T
T / 2
T / 2
T x (n - 1) / n
T x (n - 1) / n
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