Advantages; Disadvantages; Raid Adg-Advanced Data Guarding - HP 345646-001 - StorageWorks NAS 2000s External Storage Server Administration Manual

Advantages

Distributed data guarding offers:

Disadvantages

Some disadvantages of distributed data guarding are:
RAID ADG—Advanced Data Guarding
RAID ADG is similar to RAID 5 in that parity information is generated (and stored) to protect
against data loss caused by drive failure. With RAID ADG, however, two different sets of
parity data are used. This allows data to still be preserved if two drives fail. As can be seen
from
constituent drives, for a total parity usage of two drives of space.
This method is most useful when data loss is unacceptable, but cost must also be minimized.
The probability that data loss will occur when configured with RAID ADG is less than when
configured with RAID 5.
Note:
installed.
Figure 26: RAID ADG (advanced data guarding) with two sets of parity data
Advanced Data Guarding technology offers the best combination of fault tolerance and usable
disk space among RAID levels.
NAS 2000s Administration Guide
High read and write performance
Protection against data loss if one drive fails
Increased usable storage capacity, since capacity equal to only one physical drive is used
to store parity information
Lower write performance than RAID 0 or RAID 1+0
Possibility of data loss if a second drive fails before data from the first failed drive has
been rebuilt
Figure 26, each set of parity data uses up a capacity equivalent to that of one of the
The ADG feature is available only with the optional Smart Array 5304/6404 Controller
B1 B2
B3 P3,4
Q5,6
P5,6
Q7,8
B7
P1,2 Q1,2
Q3,4
B4
B5 B6
P7,8
B8
Storage Management Overview
51