Comparing Raid Levels - Impediment RS-1600-X24 User Manual

RS-1600-X24 User Guide
A.2 Comparing RAID Levels
Table 1–2
Table 1–2

Comparing RAID levels

RAID Level Min No. of
Drives
RAID 0 2
RAID 1 2
RAID 2 N/A
RAID 3 3
RAID 4 (Not 3
widely used)
RAID 5 3
RAID 50 6
92
illustrates the differences between the different RAID levels.
Description
Data striping without
redundancy
Disk mirroring
No practical use
Block-level data striping
with dedicated parity
drive
Block-level data striping
with dedicated parity
drive
Block-level data striping
with distributed parity
Combination of RAID 0
(data striping) and
RAID 5 with distributed
parity
Strengths
Highest performance
Very high:
Performance
Data protection
Minimal penalty on write
performance
Previously used for RAM
error environments
correction (known as
Hamming Code) and in disk
drives before the use of
embedded error correction
Excellent performance for
large, sequential data
requests
Data striping supports
multiple simultaneous read
requests
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
Better random performance
and data protection than
RAID 5; supports more
drives than RAID 5
Weaknesses
No data protection—one drive
fails, all data is lost
High redundancy cost
overhead—because all data is
duplicated, twice the storage
capacity is required
No practical use—same
performance can be achieved by
RAID 3 at lower cost
Not well-suited for transaction-
oriented network applications;
single parity drive does not
support multiple, concurrent write
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
Write performance is slower than
RAID 0 or RAID 1
Lower storage capacity than
RAID 5