What Is Load Balancing
What Is Load Balancing?
All hardware has its limits, and often the same service has to be spread over several machines, so as not to become congested. These solutions can be specialize in small groups on which it is a load balancing: CPU usage, storage, or network. Either one introduces the concept of clustering, or server farm, since the balance will probably be done to multiple servers. In computer networking, load balancing is a technique to distribute the workload evenly among two or more computers, network links, CPUs, hard disks or other resources to optimize resource utilization, maximize performance, minimize the response time and prevent overloading. Using multiple components with load balancing, instead of a single component, may increase reliability through redundancy.
Load balancing in computer
In the distributed computing intensive calculations, or large amounts of queries are managed using load balancing over multiple concurrent systems. This can have very different characteristics. A simple load balancing takes place, for example, on computers with multiple processors. Each process can be run on a dedicated processor. The nature of the distribution of processes on processors can thereby have a major impact on the overall performance of the system because, for example, the cache content is local to each processor.
Another method is found in computer clusters. Here, several computers are brought together so that they behave mostly like a single external system. This is done using server load balancing process. Some possible methods are the pre-connecting a computer, which divides the questions or the use of DNA with the round-robin fashion.
Load distribution is also in data / voice lines. However, there are common problems in the process of distributing the data / voice traffic equally on both lines.
Load distribution takes place even with large server farms that serve, for example, the response of HTTP requests. There are upstream systems (front-end server) to distribute according to established criteria, the individual requests to the backend server. This additional information from the HTTP request can be used to send any to a session with a user packets belonging to the same server. This is also important when using SSL to encrypt the communication so that not every request a new SSL handshake must be performed. A good implementation of a load balancing requires more information on the load exerted on the target systems.
The term load balancing in the broadest sense, a mechanism for understanding resilience: by building a cluster of computers and the distribution of requests for individual systems, we reach an increase in reliability, unless the failure of one system detected and the requests are automatically delivered to another system.
Balancing storage
Balancing of the storage medium to distribute access to file systems across multiple disks (software / hardware RAID), by deriving obvious gains in access times. These solutions can be used or exist in each of the servers in the cluster.
Load Balancing Solutions
- RAID
- Storage Area Network
Balancing network
Balancing the use of the network occurs mainly by forwarding traffic through alternative routes to ease the access to the servers. This balancing can occur at any level of the OSI layer.
An example of a site which uses techniques of load balancing is the very Wikimedia Foundation and its projects. In June 2004, the load was balanced using a combination of:
- Round robin DNS, which distributes the requests evenly to one of three Squid cache servers;
- These caching servers use the response times to distribute the applications for each of the seven server’s pages. On average, the servers already have Squid cached pages sufficient to meet 75% of the requests without even consulting the server pages;
- The PHP script that make the application distribute the load for a multi-server database on the type of application, with updates going to a primary server and the queries to one or more secondary servers.
Study: From Wikipedia, the free encyclopedia. The text is available under the Creative Commons.
