Choosing A Raid Method - HP Smart Array -UX 11i v2 Support Manual

ADG (RAID 6)
RAID 60 (RAID 6+0)
For a detailed description of the RAID levels supported by Smart Array Controllers, see the RAID
Technology Overview at http://www.hp.com/go/hpux-iocards-docs.
Click the link for your HP-UX version. The document is listed alphabetically in the "User guide"
section.
For detailed information on the probability of a logical drive failure, see

Choosing a RAID method

Use this table to select the best RAID method for your needs.
Table 14 Comparing RAID methods
RAID level
0
1
1+0
5
50
ADG
60
* Does not include online spares.
Use this table to determine which RAID modes are supported by each Smart Array controller:
Table 15 Supported RAID modes, by controller
Controller
P400
P41 1
P700m
P71 1m
The rebuilt data is typically written to online spare physical disks. If
a second physical disk fails before the data from the initial physical
disk failure is rebuilt on the online spare disk, the logical drive fails
and data is lost.
An ADG configuration has a minimum of four physical disks, plus
one or more online spares. ADG is similar to RAID 5, except that in
an ADG configuration the parity data is duplicated on two physical
disks instead of one. ADG uses this "distributed double parity" scheme
to rebuild data if as many as two physical disks fail. If a third disk
fails before the data is rebuilt on the online spare disks, the logical
drive fails and data is lost.
Similar to RAID 50, RAID 60 is a RAID 0 array striped across RAID
ADG elements. It uses the RAID ADG distributed double parity scheme
to rebuild data if as many as two physical disks fail per RAID ADG
parity group. The rebuilt data is typically written to online spare
physical disks. If a third disk in an ADG parity group fails before the
data is rebuilt on the online spare disks, the logical drive fails and
data is lost.
Minimum disks
Fault tolerance required*
No 2
Yes 2
Yes 4
Yes 3
Yes 6
Yes 4
Yes 8
RAID 0 RAID 1
Yes Yes
Yes Yes
Yes Yes
Yes Yes
Disk utilization
100%
50%
50%
67% to 94%
67% to 94%
50% to 88%
50% to 88%
RAID 1+0 RAID 5
Yes Yes
Yes Yes
Yes Yes
Yes
Appendix B (page
Read performance Write performance
High High
Intermediate Intermediate
Intermediate Intermediate
High Low
High Low
Intermediate Low
Intermediate Low
RAID 50 RAID ADG
Yes
Yes
Yes Yes
Choosing a RAID method
109).
RAID 60
Yes
21