Installation guide

G-6 AcceleRAID Installation Guide
Level 0+1. Combines RAID 0 striping and RAID 1 mirroring. This level
provides redundancy through mirroring. (Mylex RAID 6)
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. (Mylex RAID 7)
Level 10. Combines RAID 0 striping and RAID 1 mirroring spanned across
multiple drive groups (super drive group). This level provides redundancy
through mirroring.
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.
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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
Replacement Table
A replacement table contains information regarding which SCSI devices
have been replaced by others through standby replacement.
Rotated XOR Redundancy
This term (also known as “parity”) refers to a method of providing complete
data redundancy while requiring only a fraction of the storage capacity of
mirroring. In a system configured under RAID 3 or RAID 5 (which require
at least three SCSI drives), all data and parity blocks are divided between the
drives in such a way that if any single drive is removed (or fails), the data on
it can be reconstructed using the data on the remaining drives. (XOR refers
to the Boolean “Exclusive-OR” operator.) In any RAID 3 or RAID 5 array,
the capacity allocated to redundancy is the equivalent of one drive.