Web farm and Network Load Balancing overview and architecture examples

Web farm and Network Load Balancing overview

After you make a Web Farm of multiple IIS Web servers within an enterprise, these servers provide a continuous, reliable Web server to users. When a web Farm receives a request from a different user to connect to a Web site, these requests are distributed to different Web servers in the Web Farm, thereby improving the efficiency of Web Access, if a Web server in the Web Farm fails to provide service to users, The Web farm also has fault tolerance by continuing to service users with other servers that are still functioning.

Schema for Web Farm

Example of a general web Farm architecture, the following figure to avoid a single point of failure to affect the normal operation of the Web Farm, so each level, such as firewalls, load balancer, iisweb server and database server are more than one, so as to provide fault-tolerant, load-balanced functionality:

1, Firewall: firewall to ensure the security of internal computers and servers.

2. Load Balancer: Load balancer (balancer) can distribute requests to connect Web sites to different Web servers in the Web farm.

3, front-end Web Farm (IIS Web Server): Multiple IIS Web servers made up of Web Farm to provide Web Access services to users.

4, back-end Database server: To store the site's settings, Web pages or other data.

Windows Server 2008r2 already has built-in Network Load Balancing functionality (Windows NLB), so you can remove the load balancer here, which enables Windows NLB on the front-end Web farm and leverages it to provide load balancing and fault tolerance.

Also because firewalls in the Mircrosof ISA server or Microsoft Forefront Threat Management Gateway (TMG) can support Web Farm through distribution rules, you can plan the web with the following diagram Farm environment.

When an external link internal Web site request is received by Isa Server or TMG, the above image is forwarded to a Web server in the Web farm for processing according to the release rule settings. ISA server or TMG also has the ability to automatically detect whether a Web server is stopping a service, so it only forwards requests to a Web server that is still functioning.

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