Redundancy; Array Types - Adaptec DuraStor 7220SS User Manual

Redundancy

Redundancy refers to the capability of preventing data loss if a disk
drive fails. Some array types give you this capability in one of two
methods:
Two identical copies—Data is written to partitions on two disk
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drives, resulting in the same data being stored in two places.
Mirror sets, for example, use this method.
Parity—Error correction information is distributed across
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partitions on three or more disk drives. The error correction
information permits the system to rebuild the data if one drive
fails. RAID 5 sets, for example, use this method.

Array Types

Table A-1 describes the most common types of arrays. Each is
described in more detail in the sections that follow.
Table A-1. Common Array Types
Array Type Strengths
Volume Set
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Stripe set
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(RAID 0)
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Mirror set
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(RAID 1)
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Low cost
Highest performance
Supports multiple
simultaneous read and
write operations
Very high data protection
Very high performance for
read-intensive
applications
Storage Concepts
Weaknesses
No data protection
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Lower performance
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than RAID sets
No data protection; if
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one disk drive fails, all
data is lost
High cost for
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redundancy overhead,
because twice the
storage capacity is
required
A-6