Glossary
regional disaster
Glossary462
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.
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 failure (SPOF) A
component of a cluster or node that, if it
fails, affects access to applications or
services. See also multiple points of
failure.
single system high availability
Hardware design that results in a single
system that has availability higher than
normal. Hardware 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 syndrome When a cluster
reforms with equal numbers of nodes at each
site, and each half of the cluster 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.
SVOL A secondary volume configured in an
XP series disk array that uses Continuous
Access. SVOLs are the secondary copies in
physical data replication with Continuos
Access on the XP.
SymCLI The Symmetrix command line
interface used to configure and manage EMC
Symmetrix disk arrays.
Symmetrix device number The unique
device number that identifies an EMC
logical volume.
synchronous data replication Each data
replication I/O waits for the preceding I/O to
complete before beginning another