HP Smart Array 6400 Series Controllers Support Guide, September 2007

RAID 5, and the two sets of parity data are calculated and written across all the drives in the
array.
RAID ADG provides an extremely high level of fault tolerance and can sustain two simultaneous
drive failures without downtime or data loss. This fault tolerance level is useful for mission-critical
data.
Q: What does the auto-fail missing disks at boot option control?
A: The auto-fail missing disks at boot option controls the power-on behavior of the
HP-UX RAID controller when some of the configured drives are missing. Auto-fail is enabled
when the first logical drive is created by the saconfig utility. You can then disable it with the
saconfig -F command.
As an example, consider the following scenario:
1. The boot volume is on a RAID logical drive.
2. The system is powered off.
3. The cable for an enclosure containing configured disks is accidentally disconnected from
the controller.
4. All disks belonging to the boot volume are still connected to the controller.
5. The system is then powered on.
If auto-fail is enabled in this scenario: During POST, the controller fails the missing disks.
Non-fault-tolerant logical drives are FAILED. Fault-tolerant logical drives either transition to
Interim Recovery (degraded) mode or to FAILED depending on the number of disks the logical
drive is missing. The system then begins booting HP-UX.
During boot, the ciss init script detects the degraded/failed logical drives and generates an
error that instructs you to run sautil. The sautil utility displays the degraded/failed logical
drives and failed disks. At this point, you can either power off the system, reconnect the disks,
and boot again; or reconnect the disks and run the sautil accept media exchange command
to change the disks and logical drives back to OK state. For more information, see “The sautil
<device_file> accept_media_xchg <logical_drive_number> Command” (page 63).
If auto-fail is disabled in the previous scenario:[HP/9000 system] The controller temporarily
disables all logical drives, including the intact boot volume. The system fails to boot.
[HP Integrity system] During POST, you can choose one of the following options:
1. Power off the system and reconnect the disks.
2. Press F1. The controller temporarily disables all logical drives, including the intact boot
volume. The system fails to boot.
3. Press F2. The system takes the same actions as system with auto-fail enabled, as previously
described.
NOTE: HP recommends that you leave auto-fail enabled if the RAID controller is in an HP/9000
system that boots from a RAID volume.
78 Frequently Asked Questions