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.
ADG (RAID 6)
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.
RAID 60 (RAID 6+0)
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.
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
Write performance
Read performance
Disk utilization
Minimum disks
required*
Fault tolerance
RAID level
High
High
100%
2
No
0
Intermediate
Intermediate
50%
2
Yes
1
Intermediate
Intermediate
50%
4
Yes
1+0
Low
High
67% to 94%
3
Yes
5
Low
High
67% to 94%
6
Yes
50
Low
Intermediate
50% to 88%
4
Yes
ADG
Low
Intermediate
50% to 88%
8
Yes
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
RAID 60
RAID ADG
RAID 50
RAID 5
RAID 1+0
RAID 1
RAID 0
Controller
Yes
Yes
Yes
Yes
Yes
P400
Yes
Yes
Yes
Yes
P411
Yes
Yes
Yes
Yes
Yes
P700m
Yes
Yes
Yes
Yes
Yes
Yes
P711m
Choosing a RAID method
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