HP XP RAID Manager Software - Manual (Page 40)

available, all commands terminate abnormally, and the host cannot issue RAID Manager commands
to the storage system. To ensure that RAID Manager operations continue when a command device
becomes unavailable, you should set one or more alternate command devices.
Because the use of alternate I/O pathing depends on the platform, 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 prevent command device failure, RAID Manager supports an alternate command
device function.
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Definition of alternate command devices. To use an alternate command device, 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. If an
alternate command device is not defined in the configuration definition file, RAID Manager
cannot switch to the alternate command device.
•
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 command device is alternated.
It is possible to alternate the command device forcibly by issuing an alternating command
provided by Continuous Access Synchronous (horcctl -C).
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Operation of alternating command. If the command device is blocked due to online
maintenance (for example, microcode replacement), the alternating command should be issued
in advance. When the alternating command is issued again after completion of the online
maintenance, the previous command device is activated again.
•
Multiple command devices on HORCM startup. If at least one command device is available
during one or more the command devices that was described to the configuration definition
file, then HORCM starts with a warning message to startup log by using available command
device. The user needs to confirm that all command devices can be changed by using horcctl
-C command option, or HORCM has been started without warning message to the HORCM
startup log.
Figure 8 Alternate command device function
Creating/editing the configuration definition file
The configuration definition file is a text file that is created and edited using any standard text
editor (for example, UNIX vi editor, Windows Notepad). The configuration definition file defines
correspondences between the server and the volumes used by the server. There is a configuration
definition file for each host server. When the RAID Manager software starts up, it refers to the
definitions in the configuration definition file.
The configuration definition file defines the devices in copy pairs, including Business Copy, Business
Copy Z, Continuous Access Synchronous, Continuous Access Synchronous Z, Snapshot, Continuous
Access Journal, and Continuous Access Journal Z pairs, and is used for host management of the
copy pairs. Business Copy, Business Copy Z, and Snapshot use the same configuration files and
commands, and the RAID storage system determines the type of copy pair based on the S-VOL
40 Installing and configuring RAID Manager