HP XP P9500 Storage - Manual (Page 17)

Figure 3 Improved assignment sequence
The command device performs the assignment of an instance through TWO phases that have
"temporary allocation (1 0)" and "actual allocation (1 1)" to the instance assignment table.
If the command device is attacked, the instance assignment table is filled with "temporary allocation
(1 0)" status. After that, the command device will detect a fault of full space as the instance
assignment, clear up all "temporary allocation (1 0)", and then reassign the required instance
automatically.
This does not require a service representative to switch the command device "OFF/ON" to clear
up the instance table.
Verifying the RAID Manager instance number
RAID Manager provides a way to verify the number of "temporary allocations (1 0)" and "actual
allocations (1 1)" on the instance table so that you can confirm validity of the RAID Manager
instance number in use. The horcctl -DI command shows the number of RAID Manager
instances since HORCM was started as follows.
Example without command device security:
# horcctl -DI
Current control device = /dev/rdsk/c0t0d0 AI = 14 TI = 0 CI = 1
Example with command device security:
# horcctl -DI
Current control device = /dev/rdsk/c0t0d0 * AI = 14 TI = 0 CI = 1
TI : NUM of temporary instances in RAID
CI : NUM of instances using current (own) instance
Alternate command device function
The RAID Manager software issues commands to the command device via the UNIX/PC raw I/O
interface. If the command device fails in any way, all RAID Manager commands are terminated
abnormally, and you cannot use any commands. Because the use of alternate I/O pathing is
platform dependent, restrictions are placed upon it. For example, on HP-UX systems, only devices
subject to the LVM can use the alternate path PV-LINK. To avoid command device failure, RAID
Manager supports an alternate command device function.
•
Definition of alternate command devices. To use an alternate command device, you must
define two or more command devices for the HORCM_CMD item in the configuration definition
file. When two or more devices are defined, they are recognized as alternate command
devices.
•
Timing of alternate command devices. When the HORCM receives an error notification in
reply from the operating system via the raw I/O interface, the alternate command device is
used. It is possible to force a switch to use the alternate the command device by issuing the
horcctl -C switch command provided by RAID Manager.
•
Operation of alternating command. If the command device is blocked due to online
maintenance, the switch command should be issued in advance. If the switch command is
RAID Manager components on the RAID storage system 17