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 Appendix B (page 109).
Choosing a RAID method
Use this table to select the best RAID method for your needs.
Table 14 Comparing RAID methods
Write performanceRead performanceDisk utilization
Minimum disks
required*Fault toleranceRAID level
HighHigh100%2No0
IntermediateIntermediate50%2Yes1
IntermediateIntermediate50%4Yes1+0
LowHigh67% to 94%3Yes5
LowHigh67% to 94%6Yes50
LowIntermediate50% to 88%4YesADG
LowIntermediate50% to 88%8Yes60
* 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 60RAID ADGRAID 50RAID 5RAID 1+0RAID 1RAID 0Controller
YesYesYesYesYesP400
YesYesYesYesP411
YesYesYesYesYesP700m
YesYesYesYesYesYesP711m
Choosing a RAID method 21
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