|
RAID
|
Minimum
|
Description
|
Strengths
|
Weaknesses
|
|
Level
|
Number
|
|||
|
|
of Drives
|
|||
|
RAID 0
|
2
|
Data striping without redundancy
|
Highest performance
|
No data protection; One drive fails, all data is lost
|
|
RAID 1
|
2
|
Disk mirroring
|
Very high performance; Very high data protection; Very minimal
penalty on write performance
|
High redundancy cost overhead; Because all data is duplicated,
twice the storage capacity is required
|
|
RAID 2
|
Not used in LAN
|
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
|
Byte-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, simultaneous read and write
requests
|
|
RAID 4
|
3 (Not widely used)
|
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, very high 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
|
|
RAID 0/1
|
4
|
Combination of RAID 0 (data striping) and RAID 1 (mirroring)
|
Highest performance, highest data protection (can tolerate
multiple drive failures)
|
High redundancy cost overhead; Because all data is duplicated,
twice the storage capacity is required; Requires minimum of four drives
|
|
RAID 1/0
|
4
|
Combination of RAID 1 (mirroring) and RAID 0 (data striping)
|
Shares the same fault tolerance as RAID 1 (the basic mirror),
but compliments said fault tolerance with a striping mechanism that can yield
very high read rates
|
High redundancy cost overhead; Because all data is duplicated,
twice the storage capacity is required; Requires minimum of four drives
|
Wednesday, February 20, 2013
Hardware RAID Levels
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