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Glossary
RAID Levels
Mylex disk array controllers support four RAID Advisory Board approved
(RAID 0, RAID 1, RAID 3, and RAID 5), two special (RAID 0+1, and
JBOD), and three spanned (RAID 10, 30, and 50) RAID levels. All DAC960,
AcceleRAID, and eXtremeRAID series controllers support these RAID
levels.
Level 0: Provides block "striping" across multiple drives, yielding higher
performance than is possible with individual drives. This level does not
provide any redundancy.
Level 1: Drives are paired and mirrored. All data is 100 percent duplicated
on a drive of equivalent size.
Level 3: Data is "striped" across several physical drives. Maintains parity
information, which can be used for data recovery.
Level 5: Data is "striped" across several physical drives. For data
redundancy, drives are encoded with rotated XOR redundancy.
Level 0+1: Combines RAID 0 striping and RAID 1 mirroring. This level
provides redundancy through mirroring.
JBOD: Sometimes referred to as "Just a Bunch of Drives." Each drive is
operated independently like a normal disk controller, or drives may be
spanned and seen as a single drive. This level does not provide data
redundancy.
Level 10: Combines RAID 0 striping and RAID 1 mirroring spanned across
multiple drive groups (super drive group). This level provides redundancy
through mirroring and better performance than Level 1 alone.
Level 30: Data is "striped" across multiple drive groups (super drive group).
Maintains parity information, which can be used for data recovery.
Level 50: Data is "striped" across multiple drive groups (super drive group).
For data redundancy, drives are encoded with rotated XOR redundancy.
Note: The host operating system drivers and software utilities remain
unchanged regardless of the level of RAID installed. The controller makes
the physical configuration and RAID level implementation.
Manual No. 775051
G-15
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