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IT Interview Questions: What are the differences between Windows Clustering, Network Load Balancing and Round Robin, and scenarios for each use?
Information Technology (IT) Interview Questions and Answers
(Continued from previous question...)
IT Interview Questions: What are the differences between Windows Clustering,
Network Load Balancing and Round Robin, and scenarios for each use?
Cluster technologies are becoming increasingly important to ensure service
offerings meet the requirements of the enterprise. Windows 2000 and Windows
Server 2003 support three cluster technologies to provide high availability,
reliability and scalability. These technologies are: NLB, CLB and Server
cluster. These technologies have a specific purpose and are designed to meet
different requirements.
Server cluster
provides failover support for
applications and services that require high availability, scalability and
reliability, and is ideally suited for back-end applications and services,
such as database servers. Server cluster can use various combinations of
active and passive nodes to provide failover support for mission critical
applications and services.
NLB
provides failover support for IP-based
applications and services that require high scalability and availability, and
is ideally suited for Web tier and front-end services. NLB clusters can use
multiple adapters and different broadcast methods to assist in the load
balancing of TCP, UDP and GRE traffic requests.
Component Load Balancing
provides dynamic load balancing of middle-tier application components that
use COM+ and is ideally suited for application servers. CLB clusters use two
clusters. The routing cluster can be configured as a routing list on the
front-end Web servers or as separate servers that run Server cluster.
Cluster technologies by themselves are not enough to ensure that high
availability goals can be met. Multiple physical locations may be necessary
to guard against natural disasters and other events that may cause complete
service outage. Effective processes and procedures, in addition to good
architecture, are the keys to high availability. Round robin is a local
balancing mechanism used by DNS servers to share and distribute network
resource loads. You can use it to rotate all resource record (RR) types
contained in a query answer if multiple RRs are found. By default, DNS uses
round robin to rotate the order of RR data returned in query answers where
multiple RRs of the same type exist for a queried DNS domain name. This
feature provides a simple method for load balancing client use of Web servers
and other frequently ueried multihomed computers.
If round robin is disabled for a DNS server, the order of the response for
these queries is based on a static ordering of RRs in the answer list as they
are stored in the zone (either its zone file or Active Directory).
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