Building Disaster Recovery Serviceguard Solutions Using Metrocluster with EMC SRDF

Glossary
A
arbitrator Nodes in a disaster recovery architecture that act as tie-breakers when all of the nodes in a data
center go down at the same time. These nodes are full members of the Serviceguard cluster and
must conform to the minimum requirements. The arbitrator must be located in a third data center
to ensure that the failure of an entire data center does not bring the entire cluster down.
asynchronous data
replication
Local I/O will complete without waiting for the replicated I/O to complete; however, it is expected
that asynchronous data replication will process the I/Os in the original order.
automatic failover Failover directed by automation scripts or software (such as Serviceguard) and requiring no
human intervention. In a Continentalclusters environment, the start-up of package recovery groups
on the Recovery Cluster without intervention.
B
BCV (Business Continuity Volume) An EMC Symmetrix term that refers to a logical device on the EMC
Symmetrix that may be merged into or split from a regular R1 or R2 logical device. It is often
used to create a snapshot of the data taken at a known point in time. Although this copy, when
split, is often consistent, it is not usually current.
C
cluster A Serviceguard cluster is a networked grouping of HP 9000 and/or HP Integrity Servers series
800 servers (host systems known as nodes) having sufficient redundancy of software and hardware
that a single failure will not significantly disrupt service. Serviceguard software monitors the health
of the nodes, networks, application services, EMS resources, and makes failover decisions based
on where the application is able to run successfully.
complex workload Complex workloads are applications that are configured using multiple inter-related packages
that are managed collectively.
consistency group A set of Symmetrix RDF devices that are configured to act in unison to maintain the integrity of
a database. Consistency groups allow you to configure R1/R2 devices on multiple Symmetrix
frames in Metrocluster with EMC SRDF.
D
data center A physically proximate collection of nodes and disks, usually all in one room.
data consistency Whether data are logically correct and immediately usable; the validity of the data after the last
write. Inconsistent data, if not recoverable to a consistent state, is corrupt.
data currency Whether the data contains the most recent transactions, and/or whether the replica database
has all of the committed transactions that the primary database contains; speed of data replication
might cause the replica to lag behind the primary copy, and compromise data currency.
data loss The inability to take action to recover data. Data loss can be the result of transactions being
copied that were lost when a failure occurred, non-committed transactions that were rolled back
as pat of a recovery process, data in the process of being replicated that never made it to the
replica because of a failure, transactions that were committed after the last tape backup when a
failure occurred that required a reload from the last tape backup. transaction processing monitors
(TPM), message queuing software, and synchronous data replication are measures that can
protect against data loss.
disaster An event causing the failure of multiple components or entire data centers that render unavailable
all services at a single location; these include natural disasters such as earthquake, fire, or flood,
acts of terrorism or sabotage, large-scale power outages.
disaster recovery The process of restoring access to applications and data after a disaster. Disaster recovery can
be manual, meaning human intervention is required, or it can be automated, requiring little or
no human intervention.
132 Glossary