Software load balancing and hardware load balancing

Now the trend of Web site development to the use of Network Load balancing with the increase of the size of the site according to different stages to use different technologies: 1. Hardware-level load balancing

This load balancing is done through hardware, and common hardware has more expensive commercial load balancers such as NetScaler, F5, Radware, and array. Hardware load balancing is an application on the OSI layer fourth (transport layer)

Its advantage is that there is a professional maintenance team to maintain these services, the disadvantage is that the cost is too large, so for the smaller network services for the moment there is no need to use; 2. Software-level load balancing

Software-level load balancing, such as Lvs/haproxy, Nginx, Linux-based open source free load balancing software. Software load Balancing is the application of OSI layer seventh (application layer). The seventh layer load Balancer controls the content of the application Layer service, and provides a high-level control method for access traffic, which is suitable for the application of the HTTP server farm. The seventh tier load balancing technique performs load balancing tasks based on the information in the header by examining the HTTP headers that flow through.

The seventh tier load balancing benefits are shown in the following areas:

1, through the detection of the HTTP header, can detect the HTTP400, 500 and 600 series of error messages, so can transparently redirect the connection request to another server, to avoid application layer failure.

2, according to the type of data flow (such as judging the packet is an image file, compressed file or multimedia file format, etc.), the data traffic to the corresponding content of the server to handle, increase system performance.

3, according to the type of connection request, such as ordinary text, images, such as static document requests, or ASP, CGI and other dynamic document requests, the corresponding request to the corresponding server to deal with, improve the system's performance and security.

Disadvantage: The seventh load balancer is limited by the protocol it supports (usually only HTTP), which restricts its application, and checking the HTTP header will consume a lot of system resources, which will affect the performance of the system.

In the case of a large number of connection requests, the load balancer device itself becomes the bottleneck of overall network performance.

In general, hardware load balancing is better than software in function and performance, but it is costly.