A load balancing algorithm controls the
circulation of approaching requests to your bunch of servers. There are various
strategies utilized to finish this, contingent upon the unpredictability of
load adjusting required, the sort of the main job, and the distribution of the
requests coming in.
Some Common methods include:-
Round Robin:--
Some Common methods include:-
Round Robin:--
The most primitive load distribution technique. In a round
robin scenario, the load balancer simply runs down the list of servers, sending
one connection to each in turn, and starting at the top of the list when it
reaches the end
Weighted Round Robin:--
It
works on the same principle as Round Robin, but the number of connections that
each machine receives over time is proportionate to a ratio weight predefined
for each machine.
For
example, the administrator can define that Server 1 can handle five times the
traffic of Servers 2, and thus the load balancer should send five requests to
Server 1 for each one request sent to Servers 2.
Least Connections
Transfers
the latest session to the server with the least connections at the time of
session initiation. To avoid latency, this method is advisable in an
environment where server capacity and resources are uniform. Least Connections
is considered problematic, as most implementations are challenged to accurately
measure actual server workload.
In
the above example Server 1 is handling only one request from (5) whereas Server
2 is handling 3 requests (2,4,6). Thus the subsequent requests will be handled
by Server 1.
Weighted Least Connections
Identical
to Least Connection, except that servers are selected based on capacity, not
just availability. For each node, the admin specifies a Connection Limit value,
and the system creates a proportional algorithm on which load balancing is
based.
Least Pending Requests
The emerging industry
standard, Least Pending Requests selects the server with the least active
sessions based on the real-time monitoring. Requires assignment of both Layer 7
and TCP profile to the virtual server.
To achieve optimal load
distribution and maximize performance, administrators must carefully weigh the
pros and cons of their load balancing algorithms of choice.
