190
DataDirect Networks EF2800 FC RAID Storage System User Guide (V 1.0)
A r r a y B a s i c s
RAID 2
N/A
No practical use
Previously used for
RAM error
environments
correction (known as
Hamming Code) and
in disk drives before
the use of embedded
error correction
No practical use—
same performance
can be achieved by
RAID 3 at lower cost
RAID 3
3
Block-level data
striping with
dedicated parity
drive
Excellent performance
for large, sequential
data requests
Not well-suited for
transaction-oriented
network applications;
single parity drive
does not support
multiple, concurrent
write requests
RAID 4 (not
widely
used)
3
Block-level data
striping with
dedicated parity
drive
Data striping supports
multiple simultaneous
read requests
Write requests suffer
from same single
parity-drive
bottleneck as RAID 3;
RAID 5 offers equal
data protection and
better performance at
same cost
RAID 5
3
Block-level data
striping with
distributed
parity
Best cost/
performance for
transaction-oriented
networks; very high
performance and data
protection; supports
multiple simultaneous
reads and writes; can
also be optimized for
large, sequential
requests
Write performance is
slower than RAID 0 or
RAID 1
Figure 76. RAID Levels Comparison
RAID Level
Min. # of
Drives
Description
Strengths
Weakness
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