Installation guide

G-6 AcceleRAID 150 Installation Guide
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have been replaced by other SCSI devices through standby replacement.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 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 5 array, the capacity
allocated to redundancy is the equivalent of one drive.
SCSI
SCSI is an acronym for “Small Computer Systems Interface,” although it is
often used in large systems. The SCSI interface supports disk drives, tape
drives, and CD-ROM drives. Narrow SCSI supports up to seven (7) devices
on a channel, and Wide SCSI, Ultra SCSI, and Ultra2 SCSI support up to 15
devices on a channel.