Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Glossary
multiple points of failure (MPOF)
Glossary434
multiple points of failure (MPOF) More
than one point of failure that can bring down
an MC/ServiceGuard cluster.
multiple system high availability
Cluster technology and architecture that
increases the level of availability by
grouping systems into a cooperative failover
design.
mutual recovery configuration A
continental cluster configuration in which
each cluster serves the roles of primary and
recovery cluster for different recovery
groups. Also known as a bi-directional
configuration.
N
network failover The ability to restore a
network connection after a failure in
network hardware when there are
redundant network links to the same IP
subnet.
notification A message that is sent
following a cluster or package event.
O
off-line data replication. Data replication
by storing data off-line, usually a backup
tape or disk stored in a safe location; this
method is best for applications that can
accept a 24-hour recovery time.
on-line data replication Data replication
by copying to another location that is
immediately accessible. On-line data
replication is usually done by transmitting
data over a link in real time or with a slight
delay to a remote site; this method is best for
applications requiring quick recovery
(within a few hours or minutes).
P
package alert Time at which a message is
sent indicating a problem with a package.
package event A package condition such as
a failure that causes a notification message
to be sent. Package events can be
accompanied by alerts, but not alarms.
Messages are for information only; the
cmrecovercl command is not enabled for a
package event.
package recovery group A set of one or
more packages with a mapping between
their instances on the Primary Cluster and
their instances on the Recovery Cluster.
physical data replication An on-line data
replication method that duplicates I/O
writes to another disk on a physical block
basis. Physical replication can be
hardware-based where data is replicated
between disks over a dedicated link (e.g.
EMC’s Symmetrix Remote Data Facility or
the HP StorageWorks E Disk Array XP
Series Continuous Access), or
software-based where data is replicated on
multiple disks using dedicated software on
the primary node (e.g. MirrorDisk/UX).
planned downtime An anticipated period
of time when nodes are taken down for
hardware maintenance, software
maintenance (OS and application), backup,
reorganization, upgrades (software or
hardware), etc.
PowerPath A host-based software product
from Symmetrix that delivers intelligent I/O
path management. PowerPath is required
for M by N Symmetrix configurations using
MetroCluster/SRDF.