Mylex DAC960PG, Installation Manual

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RAID Management
2-12 DAC960PG Installation Guide
RAID Management
RAID is an acronym for Redundant Array of Independent Disks. The
DAC960PG controller implements several different versions of the Berkeley
RAID technology, and two special versions that are specific only to the
DAC960 family of RAID controllers. Each version (referred to as a RAID
Level) that is supported by the DAC960PG is shown in Table 2-2.
An appropriate RAID level is selected when the logical drives are defined or
created using a configuration software utility such as DACCF. Deciding
which RAID level to use is based on the following priorities:
An appropriate RAID level is selected when the logical units are defined or
created. This decision is based on disk capacity, data availability (fault
tolerance or redundancy), and disk performance.
The DAC960PG makes the RAID implementation and the disks’ physical
configuration transparent to the host operating system. This means that the
host operating system drivers and software utilities are not affected,
regardless of the RAID level selected.
Correct installation of the disk array and the DAC960PG requires a proper
understanding of RAID technology and the concepts described in this
chapter and in the DACCF Utilities documentation.
Table 2-2.
Supported RAID Levels
RAID
Level Description
Drives/Group
Min Max
0 Block striping is provided, which yields higher perform-
ance than with individual drives. There is no
redundancy. 2 8
1 Drives are paired and mirrored. All data is 100% dupli-
cated on an equivalent drive (fully redundant). 2 2
3 Data is striped across several physical drives. Parity
protection is used for data redundancy. 3 8
5 Data is striped across several physical drives. Parity
protection is used for data redundancy. 3 8
0+1 Combination of RAID levels 0 and 1 (Mylex RAID 6).
Provides striping and redundancy through mirroring. 3 8
JBOD “Just a Bunch of Disks (Mylex RAID 7).” Each drive
operates independently like with a common host bus
adapter. No redundancy is provided. 1 1