6.4

VMware, Inc. 91
Glossary
Shared Nothing
A key vCenter Server Heartbeat feature whereby hardware is not shared between the Primary and
Secondary servers, thus preventing a single point of failure.
SMTP
A TCP/IP protocol used in sending and receiving e-mail between or among servers.
Split-brain Avoidance
A unique feature of vCenter Server Heartbeat that uses various checks to overcome a scenario where both
Primary and Secondary servers attempt to become active at the same time, leading to an active-active
rather than an active-passive model.
Split-brain Syndrome
A situation where both the Primary and Secondary servers in a vCenter Server Heartbeat server pair are
operating in the active mode and attempting to service clients, causing different data updates to be
applied independently to each server.
SSL
(Secure Sockets Layer) establishes a secure session by electronically authenticating each end of an
encrypted transmission.
Subnet
A division of a network into an interconnected but independent segment or domain, to improve
performance and security.
Storage Area Network (SAN)
A high-speed special-purpose network or (sub-network) that interconnects different kinds of data storage
devices with associated data servers on behalf of a larger network of users.
Switchover
The graceful transfer of control and application service to the passive server.
Synchronize
The internal process of transporting 64KB blocks of changed files or registry key data, through the
VMware Channel from the active server to the passive server. The data on the passive server is a mirror
image of the protected data on the active server, a required condition for data replication on a vCenter
Server Heartbeat server pair.
System State
Data that comprises the registry, COM+ Class Registration database, files under Windows File Protection,
and system boot file. Other data can be included in the system state data.
T Task
An action performed by vCenter Server Heartbeat when defined conditions are met.
Time-To-Live (TTL)
The length of time that a locally cached DNS resolution is valid. The DNS server must be re-queried after
the TTL expires.
Traceroute
A utility that records the route through the Internet between the computer and a specified destination
computer.
U Ungraceful (Unclean) Shutdown
A shutdown of vCenter Server Heartbeat resulting from a critical failure or by shutting down Windows
without first performing a proper shutdown of vCenter Server Heartbeat, resulting in possible data loss.