DNS轮循
  DNS轮循是指将相同的域名解释到不同的IP,随机使用其中某台主机的技术。但其具有明显的缺点:一旦某个服务器出现故障,即使及时修改了DNS设置,还是要等待足够的时间(刷新时间)才能发挥作用,在此期间,保存了故障服务器地址的客户计算机将不能正常访问服务器。DNS负载均衡采用的是简单的轮循负载算法,不能区分服务器的差异,不能反映服务器的当前运行状态,不能做到为性能较好的服务器多分配请求,甚至会出现客户请求集中在某一台服务器上的情况。

  F5 BIG-IP
点击在新窗口中浏览此图片  简介:F5 Networks 公司的著名硬件负载均衡交换机。支持硬件四层、七层交换。不同的型号性能不同,BIG-IP 6400可以支持800万条并发连接,低一点型号的可以支持400万条以上的并发连接。性能极高,但价格也不菲。
  价格:BIG-IP 6400的价格在16万元人民币左右。
  网址:http://www.f5.com.cn/(中国) http://www.f5.com/(全球)

  LVS(Linux Virtual Server)
  简介:软件四层交换。LVS是在Linux内核中作四层交换,只花128个字节记录一个连接信息,不涉及到文件句柄操作,故没有65535最大文件句柄数的限制。LVS性能很高,可以支持100~400万条并发连接。
  价格:免费、开源
  网址:http://zh.linuxvirtualserver.org/

  L7SW(Layer7 switching)
  简介:软件七层交换。这是一款类似LVS的新负载均衡软件,我没有实际应用过,性能未知,因此不作评价。这是它的英文介绍:Layer7 switching is driving a low-level engine using networking design to speed-up forwarding of data stream. Implementation in this project is split into a userspace daemon and a low-level kernelspace forwarding engine. Userspace daemon is responsible for scheduling and switching decisions. Kernelspace forwarding engine is responsible for forwarding stream and using TCP-Splicing scheme. TCP-Splicing is the postponement of the connection between the client and the server in order to obtain sufficient information to make a routing decision. This project is close to Linux Virtual Server project since lot of discusions on this topics have been made online and offline LVS project.
  价格:免费、开源
  网址:http://www.linux-l7sw.org/

  HAProxy
  简介:软件七层交换,反向代理服务器。目前还不支持虚拟主机,但其配置简单,拥有非常不错的服务器健康检查功能,当其代理的后端服务器出现故障,HAProxy会自动将该服务器摘除,故障恢复后再自动将该服务器加入。另外,HAProxy还支持双机热备。我曾经用过一段时间,能支持2~3万条并发连接。现在我用它做普通的小并发负载均衡,主要用到的是它的服务器健康检查功能。
  价格:免费、开源
  网址:http://haproxy.1wt.eu/

  Nginx
  简介:软件七层交换,反向代理服务器。能够很好地支持虚拟主机,可配置性很强,可以按URL做负载均衡。我目前一直在用,大约能支持3~5万条并发连接。
  价格:免费、开源
  网址:http://wiki.codemongers.com/NginxChs(中文维基)


技术大类 » 其他Unix技术 | 评论(36) | 引用(1) | 阅读(60277)
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