Managing HP Serviceguard A.12.00.00 for Linux, June 2014

For more information about how to create a storage infrastructure with VxVM, see Creating a
Storage Infrastructure with VxVM.
3.6.4.1 Limitations
Following are the limitations of VxVM:
• Serviceguard does not support VxVM with VMs (Virtual Machines).
• Serviceguard does not support VxVM on iSCSI storage.
• Serviceguard supports VxVM only with OS Native naming scheme. To set the OS Native
naming scheme:
#/usr/sbin/vxddladm set namingscheme=osn
3.7 About Persistent Reservations
Serviceguard for Linux packages use persistent reservations (PR) to control access to LUNs. Persistent
reservations, defined by the SCSI Primary Commands version 3 (SPC-3) standard, provide a means
to register I/O initiators and specify who can access LUN devices (anyone, all registrants, only
one registrant) and how (read-only, write-only).
Unlike exclusive activation for volume groups, which does not prevent unauthorized access to the
underlying LUNs, PR controls access at the LUN level. Registration and reservation information is
stored on the device and enforced by its firmware; this information persists across device resets
and system reboots.
NOTE: Persistent Reservations coexist with, and are independent of, activation protection of
volume groups. You should continue to configure activation protection as instructed under Enabling
Volume Group Activation Protection. Subject to the Rules and Limitations spelled out below, Persistent
Reservations will be applied to the cluster's LUNs, whether or not the LUNs are configured into
volume groups.
Advantages of PR:
• Consistent behavior.
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.
3.7.1 Rules and Limitations
Serviceguard automatically implements PR for packages that use LUN storage, subject to the
following constraints:
• You can use PR with the following restrictions:
PR is supported with Device Mapper (DM) multipath in the modular package.◦
◦ During package startup, Serviceguard performs registration only on active paths. If the
path becomes active after package startup, it remains unusable until the package is
restarted.
◦ If you are not using the udev alias names, multipath physical volumes names must be in
the /dev/mapper/XXXX or /dev/mpath/XXXX format.
3.7 About Persistent Reservations 71