Managing HP Serviceguard for Linux, Tenth Edition, September 2012

Advantages of PR are:
• Consistent behavior.
Whereas different volume managers may implement exclusive activation differently
(or not at all) PR is implemented at the device level and does not depend on
volume-manager support for exclusive activation.
• Packages can control access to LUN devices independently of a volume manager.
Serviceguard's support for the OCFS2 file system and ASM manager allows packages
whose applications use these protocols to access storage devices directly, without
using a volume manager.
Rules and Limitations
Serviceguard automatically implements PR for packages that use LUN storage, subject
to the following constraints:
• The LUN device must support PR and be consistent with the SPC-3 specification
• PR is not available in legacy multi-node packages.
PR is available in modular multi-node packages, and in both modular and legacy
failover packages.
◦ All instances of a modular multi-node package must be able to use PR; otherwise
it will be turned off for all instances.
• The package must have access to real devices, not only virtualized ones.
This means that HPVM guests running as cluster nodes cannot use PR.
84 Understanding Serviceguard Software Components