Managing HP Serviceguard for Linux, Tenth Edition, September 2012

NOTE: PR is turned off at the cluster level if any node is an HPVM guest.
• Clusters that have nodes that are VMware guests can use PR, with the following
restrictions:
◦ Two or more VMware guests acting as nodes in the same cluster cannot run on
the same host.
(A cluster can have multiple VMware guests if each is on a separate host; and
a host can have multiple guests if each is in a different cluster.)
◦ Packages running on VMware guests must use Raw Device Mapping to access
the underlying physical LUNs.
CAUTION: Serviceguard makes and revokes registrations and reservations during
normal package startup and shutdown, or package failover. Serviceguard also provides
a script to clear reservations in the event of a catastrophic cluster failure. You need to
make sure that this script is run in that case; the LUN devices could become unusable
otherwise. See “Revoking Persistent Reservations after a Catastrophic Failure” (page 292)
for more information.
How Persistent Reservations Work
You do not need to do any configuration to enable or activate PR, and in fact you cannot
enable it or disable it, either at the cluster or the package level; Serviceguard makes the
decision for each cluster and package on the basis of the Rules and Limitations described
above.
When you run cmapplyconf (1m) to configure a new cluster, or add a new node,
Serviceguard sets the variable cluster_pr_mode to either pr_enabled or
pr_disabled.
• ENABLED means that packages can in principle use PR, but in practice will do so
only if they meet the conditions spelled out under “Rules and Limitations”.
• DISABLED means that no packages can use PR because at least one node is an
HPVM guest.
You can see the setting of cluster_pr_mode in the output of cmviewcl -f line;
for example:
...
cluster_pr_mode: pr_enabled
NOTE: You cannot change the setting of cluster_pr_mode.
If a package is qualified to use PR, Serviceguard automatically makes and revokes
registrations and reservations for the package's LUNs during package startup, and
About Persistent Reservations 85