flyinweb's blog

At Gigahost we are managing a lot of mailboxes for our users.

At the moment these are all located on one high speced server with the outgoing SMTP split to another server.

We allow our users to connect via both IMAP and POP3 and support STARTTLS on ports 110/143 and SSL/TLS on ports 993/995.

Since we are constantly adding new users and these in turn add new mailboxes we are running out of options as to upgrade the current server. Hosting mailboxes via Courier, Dovecot or similar is very IO intensive and therefore in the long run disk IO becomes a problem.

The solution to this is ofcourse to scale the setup to more servers. Some hosting providers do this by simply adding users to a new mail server eg. mail2.example.com, mail3.example.com and so on.

What we would like to do is use a reverse proxy so that the user always connects to mail.gigahost.dk and the proxy ensures that the user is send to the correct server.

1、Using a php script on apache server as the auth backend

Start with the configuration from NginxImapProxyExample. For detail information about different configuration parameters, see the NginxMailCoreModule page.

1. Your Proxy server for pop/imap is running on 192.168.1.1
2. You have 2 backend pop/imap servers: 192.168.1.22 and 192.168.1.33
3. You have a webserver that you will use for the authentication and redirection logic 192.168.1.44.
4. The authentication script is /mail/auth.php

How do I configure nginx as failover reverse proxy load balancer in front of two Apache web servers under CentOS / RHEL 5.x?

nginx is a Web and Reverse proxy server. Nginx used in front of Apache Web servers. All connections coming from the Internet addressed to one of the Web servers are routed through the nginx proxy server, which may either deal with the request itself or pass the request wholly or partially to the main web servers.

本文在介绍 squid 反向代理的工作原理的基础上，指出反向代理技术在提高网站访问速度，增强网站可用性、安全性方面有很好的用途。作者在具体的实验环境下，利用 DNS 轮询和 Squid 反向代理技术，实现了网站的负载均衡，从而提高了网站的可用性和可靠性。

现在有许多大型的门户网站如 SINA 都采用 squid 反向代理技术来加速网站的访问速度，可将不同的 URL 请求分发到后台不同的 WEB 服务器上，同时互联网用户只能看到反向代理服务器的地址，加强了网站的访问安全。