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在调度器的实现技术中，IP负载均衡技术是效率最高的。在已有的IP负载均衡技术中有通过网络地址转换（Network Address Translation）将一组服务器构成一个高性能的、高可用的虚拟服务器，我们称之为VS/NAT技术（Virtual Server via Network Address Translation），大多数商品化的IP负载均衡调度器产品都是使用此方法，如Cisco的LocalDirector、F5的Big/IP和Alteon的ACEDirector。在分析VS/NAT的缺点和网络服务的非对称性的基础上，我们提出通过IP隧道实现虚拟服务器的方法VS/TUN（Virtual Server via IP Tunneling），和通过直接路由实现虚拟服务器的方法VS/DR（Virtual Server via Direct Routing），它们可以极大地提高系统的伸缩性。所以，IPVS软件实现了这三种IP负载均衡技术，它们的大致原理如下

支持海量域名的dns架构

环境 操作系统： Redhat 5.2 64位

dns服务器：bind9.5.0-p1

数据库： mysql5.1

利用keepalived 实现HA&LB

Introduction

DNS (Domain Name Service) is one of the primary Internet services, which is to map human-friendly domain names to machine-friendly IP address. If there are a lot of people using DNS service (for example, subscribers use ISP's DNS server), one DNS server might be becoming a bottleneck, and the server might fail.

Scalable DNS cluster can help provide scalability and availability of DNS service.

The Example below is about setting up a cluster for recursive DNS but you can just as well use the same method for authorative DNS as well. Just remember that clients who use your cluster as a secondary nameservice would need to also-notify{} each of your realservers, not just the service-IP.

实现Kickstart + NFS + DHCP + PXE的全自动远程无人值守安装：

                           -------------------
                                 HAProxy
                           Architecture  Guide
                           -------------------
                             version 1.1.34
                              willy tarreau
                               2006/01/29

JVM内存JAVA_OPTS参数

最近几个月，做的性能测试项目中，发现了一些内存方面的问题，其中有涉及到对JBOSS里的JAVA_OPTS配置，例如一下所示；
JAVA_OPTS=”-server -Xms1536m -Xmx1536m -XX:NewSize=320m -XX:MaxNewSize=320m -XX:PermSize=96m -XX:MaxPermSize=256m -Xmn500m -XX:MaxTenuringThreshold=5″
JAVA_OPTS并不是已成不变的，不同的应用、软硬件环境下，要想充分发挥应用的性能，这些参数里边的设置可是非常有技巧和具有经验积累的。
经过查找资料，先看下JAVA_OPTS参数表示的意义。

In this document I use Debian Sarge for all nodes. Therefore the setup might differ a bit for other distributions. The MySQL version I use in this setup is 5.0.19. If you do not want to use MySQL 5, you can use MySQL 4.1 as well, although I haven't tested it.

This howto is meant as a practical guide; it does not cover the theoretical backgrounds. They are treated in a lot of other documents in the web.

This document comes without warranty of any kind! I want to say that this is not the only way of setting up such a system. There are many ways of achieving this goal but this is the way I take. I do not issue any guarantee that this will work for you!