Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access EVA A.05.01

quorum server A cluster node that acts as a tie-breaker in a disaster tolerant architecture in case all of the nodes
in a data center go down at the same time. See also arbitrator.
R
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.
S
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.
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.
T
transparent
failover
A client application that automatically reconnects to a new server without the user taking any
action.
transparent IP
failover
Moving the IP address from one network interface card (NIC), in the same node or another node,
to another NIC that is attached to the same IP subnet so that users or applications may always
specify the same IP name/address whenever they connect, even after a failure.
U,V,Z
virtual array Synonymous with disk array and storage system; a group of disks in one or more disk enclosures
combined with control software that presents disk storage capacity as one or more virtual disks.
See also virtual disk. See also virtual disk.
Virtual Controller
Software (VCS)
See controller software.
virtual disk Variable disk capacity that is defined and managed by the array controller and presented to
hosts as a disk. May be called Vdisk in the user interface.
volume group In LVM, a set of physical volumes such that logical volumes can be defined within the volume
group for user access. A volume group can be activated by only one node at a time unless you
are using Serviceguard OPS Edition. Serviceguard can activate a volume group when it starts a
package. A given disk can belong to only one volume group. A logical volume can belong to
only one volume group.
Vraid The level to which user data is protected. Redundancy is directly proportional to cost in terms of
storage usage; the greater the level of data protection, the more storage space is required. See
also: Vraid0, Vraid1, Vraid5, Vraid6.
Vraid0 Optimized for I/O speed and efficient use of physical disk space, but provides no data
redundancy.
Vraid1 Optimized for data redundancy and I/O speed, but uses the most physical disk space.
Vraid5 Provides a balance of data redundancy, I/O speed, and efficient use of physical disk space.
Vraid6 Offers the features of Vraid5 while providing more protection for an additional drive failure, but
uses additional physical disk space.
134 Glossary