HP XP7 Disk Array Configuration Guide (H6F56-96003)

Setting the UUID
HP recommends that OpenVMS customers use host mode option 33 to enable the UUID feature.
This increases the capabilities for OpenVMS hosts that access the disk array, by:
• Allowing the presentation of CU:LDEVs before 7F:FF to the OpenVMS hosts.
• Allowing the OpenVMS system administrator to define the DGA device number to present to
the OpenVMS host.
If use of host mode option 33 is enabled after devices are already presented to an OpenVMS
host, HP recommends rebooting the OpenVMS host. Though SYSMAN IO AUTO can be used to
discover new DGA devices, this helps avoid problems with stale data structures within OpenVMS.
SAN boot and UUID with OpenVMS. The UUID can be used with OpenVMS for Integrity servers.
This includes the system disk, quorum disk, and DOSD volumes. However for OpenVMS AlphaServer
hosts, the UUID for those volumes must be set to the decimal value of the hexadecimal value of the
CU:LDEV value. If the CU:LDEV value is 01:FF, then the UUID must be set to 511 (the decimal value
of 01FF). Thus, none of these volumes can have a CU:LDEV value greater than 7F:FF. Additionally,
these volumes must use LUN numbers 1 to 255. These are limitations of the AlphaServer firmware
used (both for the definition of known paths by the wwidmgr and by the boot code).
If host mode option 33 is not set, then the default behavior is to present the volumes to the OpenVMS
host by calculating the decimal value of the hexadecimal CU:LDEV value. That calculated value
will be the value of the DGA device number.
CAUTION:
• The UUID (or by default the decimal value of the CU:LDEV value) must be unique across the
SAN for the OpenVMS host and/or OpenVMS cluster. No other SAN storage controllers
should present the same value. If this value is not unique, data loss will occur.
• If host mode option 33 is not set, none of the OpenVMS LUNs can have a CU:LDEV value
greater than 7F:FF. That hexadecimal value equals decimal 32767, which is the largest DGA
device number allowed by OpenVMS.
• If host mode option 33 is set and the UUID for the LUN is not set, then the device will NOT
be presented to the OpenVMS host. If configuration problems arise, use the
SYS$ETC:FIBRE_SCAN program to search for devices that are presented to the OpenVMS
host.
Use the following procedure to set the UUID.
1. Start LUN Manager and display the LUN Manager window (see Figure 4 (page 44)).
Figure 4 LUN Manager window (OpenVMS)
44 OpenVMS