regional disaster

A disaster, such as an earthquake or hurricane, that affects a large region. Local, campus, and

 

proximate metropolitan clusters are less likely to protect from regional disasters.

rehearsal package

The recovery cluster package used to validate the recovery environment and procedure as part

 

of a rehearsal operation.

remote failover

Failover to a node at another data center or remote location.

resynchronization

The process of making the data between two sites consistent and current once systems are restored

 

following a failure. Also called data resynchronization.

rolling disaster

A second disaster that occurs before recovering from a previous disaster, for example, while data

 

is being synchronized between two data centers after a disaster, one of the data centers fails,

 

interrupting the data synchronization process. Rolling disasters may result in data corruption that

 

requires a reload from tape backups.

S

 

 

single point of

A component of a cluster or node that, if it fails, affects access to applications or services. See

failure (SPOF)

also multiple points of failure.

single system high

Hardware design that results in a single system that has availability higher than normal. Hardware

availability

design examples are:

 

•

n+1 fans

 

•

n+1 power supplies

 

•

multiple power cords

 

•

on-line addition or replacement of I/O cards, memory, etc.

special device file

The device file name that the HP-UX operating system gives to a single connection to a node, in

 

the format /dev/devtype/filename.

split-brain

When a cluster reforms with equal numbers of nodes at each site, and each half of the cluster

syndrome

thinks it is the authority and starts up the same set of applications, and tries to modify the same

 

data, resulting in data corruption. Serviceguard architecture prevents split-brain syndrome in all

 

cases unless dual cluster locks are used.

SRDF

(Symmetrix Remote Data Facility) A level 1-3 protocol used for physical data replication between

 

EMC Symmetrix disk arrays.

sub-clusters

Sub-clusters are clusterwares that run above the Serviceguard cluster and comprise only the nodes

 

in a Metrocluster site. Sub-clusters have access only to the storage arrays within a site.

SVOL

A secondary volume configured in an P9000 or XP series disk array that uses Continuous Access.

 

SVOLs are the secondary copies in physical data replication with Continuos Access on the P9000

 

or XP.

SymCLI

The Symmetrix command line interface used to configure and manage EMC Symmetrix disk

 

arrays.

Symmetrix device

The unique device number that identifies an EMC logical volume.

number

 

 

synchronous data

Each data replication I/O waits for the preceding I/O to complete before beginning another

replication

replication. Minimizes the chance of inconsistent or corrupt data in the event of a rolling disaster.

T

 

 

transaction

Software that allows you to modify an application to store in-flight transactions in an external

processing monitor

location until that transaction has been committed to all possible copies of the database or

(TPM)

filesystem, thus ensuring completion of all copied transactions. A TPM protects against data loss

 

at the expense of the CPU overhead involved in applying the transaction in each database replica.

 

Software that provides a reliable mechanism to ensure that all transactions are successfully

 

committed. A TPM may also provide load balancing among nodes.

transparent

A client application that automatically reconnects to a new server without the user taking any

failover

action.

520 Glossary