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Technology has completely changed the modern life standard and web services play crucial part in this technology. Internet is one such service that has connected us all in a way that was barely imaginable.with this outstanding progress in computer technology the demand of high speed processing has risen and so the need of high scalability, availability and rapid response. Today millions of users use internet, this rapid growth has lead to the storage of tremendous amount of data and rise in web traffic. This has further lead to the problems of network congestion, web service delay and slow response time.These factors increased the trend of using distributed systems.. To increase the efficiency of network multiple servers are deployed connected to each other to form a server farm. Client request is transferred to one of the back end server in the server farm. It replies to client request without the client ever knowing about the internal distribution. The process of distributing the client request among servers is performed by load balancing technique.
Load balancing is the way of distributing
loadunits across a set of processors which
are connected to a network which may be
distributed across the globe. The excess load
or remaining unexecuted load from a processor
is migrated to otherprocessors which have
load below the threshold load .Thresholdload
is smuch an amount of load to a processor
that any load may comefurther to that processor.
In a system with multiple nodes there is a
very high chance that some nodes will be
idle while the other will be over loaded.
BENEFITS
a. Load balancing improves the
performance of each node and
hence the overall system performance
b)Load balancing reduces the job idle time
c)Small jobs do not suffer from long starvation
d)Maximum utilization of resources
e)Response time becomes shorter
f)Higher throughput
g)Higher reliability
h)Low cost but high gain
i)Extensibility and incremental growth
STATIC LOAD BALANCING
static algorithm the processes are assigned to the processors
at thecompile time according to the performance of the nodes.
Once the processes are assigned, no change or
reassignment is possible at the run time. Number of
jobs in each node is fixed in static load
balancing algorithm. Static algorithms do not
collect any information about the nodes The assignment of
jobs is done to the processing nodes on the
basis of the following factors: incoming time, extent of resource
needed, mean execution time and inter-process communications. Since
these factors should be measured before the assignment,
this is why static load balance is also called probabilistic algorithm.
As there is no migration of job at the runtime no overhead occurs or
a little over head may occur In static load balancing it
is observed that as the number of tasks is more than the
processors, better will be the load balancing
During the static load balancing too much
information about the system and jobs must
be known before the execution. These information
may not be available in advance. A thorough study
on the system state and the jobs quite tedious approach
in advance. So, dynamic load balancing algorithm came into
existence. The assignment of jobs is done at the runtime.
In DLB jobs are reassigned at the runtime depending upon
the situation that is the load will be transferred from heavily
Loaded nodes to the lightly loaded nodes [7, 10, 12]. In this case
communication over heads occur and becomes more when number of
processors increase. In International Journal of Computer Science &
Engineering Survey April 2012 23 dynamic load balancing no decision
is taken until the process gets execution. This strategy collects
the information about the system state and about the job information.