Advanced Data Guarding Option Software Reference Guide

Compaq Advanced Data Guarding Option Software Reference Guide 1-1
COMPAQ CONFIDENTIAL
Writer: John Turner File Name: b-ch1 overview of RAID ADG
Codename: adg2 Part Number: 283954-001 Last Saved On: 5/22/02 12:41 PM
1
Overview of RAID ADG
Advanced Data Guarding (RAID ADG) is a fault-tolerance method that uses two
different and independent sets of parity data. A logical volume using this
exceptionally high level of data protection can tolerate the simultaneous failure of
two hard drives without suffering downtime or data loss.
B1
B3
P5,6
Q7,8
B2
B7
P3,4
Q5,6
B5
B8
P1,2
Q3,4
B4
B6
P7,8
Q1,2
Figure 1-1: Array using RAID ADG, showing data blocks
(B) and two parity data sets (P, Q)
RAID ADG also makes efficient use of drive space, since the two sets of parity data
occupy a total drive space equivalent to two hard drives. The amount of drive space
used for parity data is independent of the total number of hard drives in the logical
volume.