Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Designing Highly Available Cluster Applications
Designing Applications to Run on Multiple Systems
Appendix B334
Give Each Application its Own Volume Group
Use separate volume groups for each application that uses data. If the
application doesn't use disk, it is not necessary to assign it a separate
volume group. A volume group (group of disks) is the unit of storage that
can move between nodes. The greatest flexibility for load balancing
exists when each application is confined to its own volume group, i.e., two
applications do not share the same set of disk drives. If two applications
do use the same volume group to store their data, then the applications
must move together. If the applications’ data stores are in separate
volume groups, they can switch to different nodes in the event of a
failover.
The application data should be set up on different disk drives and if
applicable, different mount points. The application should be designed to
allow for different disks and separate mount points. If possible, the
application should not assume a specific mount point.
Use Multiple Destinations for SNA Applications
SNA is point-to-point link-oriented; that is, the services cannot simply
be moved to another system, since that system has a different
point-to-point link which originates in the mainframe. Therefore, backup
links in a node and/or backup links in other nodes should be configured
so that SNA does not become a single point of failure. Note that only one
configuration for an SNA link can be active at a time. Therefore, backup
links that are used for other purposes should be reconfigured for the
primary mission-critical purpose upon failover.