Comparing Raid Levels - Rorke Data The Galaxy 65 User Manual

Galaxy 65 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 Strengths
Data striping without Highest performance
redundancy
Disk mirroring Very high:
Performance
Data protection
Minimal penalty on write
performance
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
Block-level data striping Excellent performance for
with dedicated parity large, sequential data
drive requests
Block-level data striping Data striping supports
with dedicated parity multiple simultaneous read
drive requests
Block-level data striping Best cost/performance for
with distributed parity transaction-oriented
networks; very high
performance and data
protection; supports multiple
simultaneous reads and
writes; can also be optimized
for large, sequential
requests
Combination of RAID 0 Better random performance
(data striping) and and data protection than
RAID 5 with distributed RAID 5; supports more
parity 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