名站DNS負載均衡技術的大曝光
在負載均衡的使用中，***理解的都是網站的域名分配了。它所使用的是DNS負載均衡技術，這項將技術基本上在各大網站上都有體現，那么為了讓大家更好的理解這個知識，我們搜集了一些名站的服務器資料，來幫助到家消化下這些內容。
1、新浪
新浪采用了ChinaCache做的CDN系統，ChinaCache在全國分布了四十多個點，同時采用基于動態分配的全球DNS負載均衡技術。
從新浪的站點結構可以看出：
> www.sina.com.cn
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: libra.sina.com.cn
Addresses: 61.135.152.71, 61.135.152.72, 61.135.152.73, 61.135.152.74 61.135.152.75, 61.135.152.76, 61.135.153.181, 61.135.153.182, 61.135.53.183, 61.135.153.184, 61.135.152.65, 61.135.152.66, 61.135.152.67, 61.135.12.68, 61.135.152.69, 61.135.152.70
Aliases: www.sina.com.cn, jupiter.sina.com.cn
在北京地區ChinaCache將www.sina.com.cn 的網址解析到libra.sina.com.cn，然后libra.sina.com.cn做了DNS負載均衡技術，將libra.sina.com.cn解析到61.135.152.71等16個ip上，這16個ip分布在北京的多臺前臺緩存服務器上，使用squid做前臺緩存。如果是在其它地區訪問http://www.sina.com.cn可能解析刮..??的效果。
我們再看一個新浪其它頻道是指到哪里的：
> news.sina.com.cn
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: libra.sina.com.cn
Addresses: 61.135.152.65, 61.135.152.66, 61.135.152.67, 61.135.152.68 61.135.152.69, 61.135.152.70, 61.135.152.71, 61.135.152.72, 61.135.152.73 61.135.153.178, 61.135.153.179, 61.135.153.180, 61.135.153.181, 61.135.153.182 61.135.153.183, 61.135.153.184
Aliases: news.sina.com.cn, jupiter.sina.com.cn
可以看出，各個頻道的前臺緩存集群與www.sina.com.cn的前臺緩存集群是相同的。#p#
2、搜狐
Sohu與新浪的DNS負載均衡技術原理差不多，下面是nslookup的結果：
> www.sohu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: pagegrp1.sohu.com
Addresses: 61.135.132.172, 61.135.132.173, 61.135.132.176, 61.135.133.109 61.135.145.47, 61.135.150.65, 61.135.150.67, 61.135.150.69, 61.135.150.74 61.135.150.75, 61.135.150.113, 61.135.150.145, 61.135.131.73, 61.135.131.91 61.135.131.180, 61.135.131.182, 61.135.131.183, 61.135.132.65, 61.135.
132.80
Aliases: www.sohu.com
只不過libra.sina.com.cn換成了pagegrp1.sohu.com
我們再來看一下sohu的頻道：
> news.sohu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: pagegrp1.sohu.com
Addresses: 61.135.145.47, 61.135.150.65, 61.135.150.67, 61.135.150.69 61.135.150.74, 61.135.150.75, 61.135.150.113, 61.135.150.145, 61.135.131.73 61.135.131.91, 61.135.131.180, 61.135.131.182, 61.135.131.183, 61.135.132.65 61.135.132.80, 61.135.132.172, 61.135.132.173, 61.135.132.176, 61.135.133.109
Aliases: news.sohu.com
同新浪相同，用的是同樣的服務器群，這可能是因為他們用的都是ChinaCache的服務吧，不過sohu的名字起的有點土，pagegrp1，沒有 libra，pavo好聽，這名字聽起來有點像法語，比較浪漫。#p#
3、網易
網易似乎沒用ChinaCache的服務，下面是nslookup結果：
> www.163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.163.com
Addresses: 202.106.168.103, 202.106.168.104, 202.106.168.109, 202.106.168.121 202.108.36.153, 202.108.36.155, 202.108.36.156, 202.108.36.167, 202.108.36.172 202.108.36.196
直接在www.163.com 這個域名上用了DNS負載均衡技術。這樣的話就要求服務器必須放的非常靠近主節點，才能保證各地的用戶訪問的速度。
但163不同的頻道是放在不同的緩存集群上的，這與sina，sohu有些不同，等于sina，sohu是按照地區劃分服務器集群，而網易按照頻道劃分服務器集群。
> 163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: 163.com
Addresses: 202.108.36.205, 202.108.36.206, 202.108.36.207, 202.108.36.201 202.108.36.202, 202.108.36.203, 202.108.36.204
顯然，這和www.163.com 不是一個集群，我們再來試一個：
> sports.163.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: channel.cache.163.com
Addresses: 202.108.36.136, 202.108.36.208, 202.108.36.209, 202.108.36.210 202.108.36.211, 202.108.36.212, 202.108.36.213
Aliases: sports.163.com
可以看出，和上面的集群也是不同的。#p#
4、百度
百度的前臺服務器就不是很多了：
> www.baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.baidu.com
Addresses: 202.108.250.249, 202.108.249.134
> baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: baidu.com
Address: 202.108.250.228
> mp3.baidu.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: mp3.baidu.com
Address: 202.108.249.131
只有www.baidu.com做了兩臺服務器的集群，頻道都用了一臺服務器做前臺#p#
5、一搜
> yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: yisou.com
Addresses: 202.165.102.114, 202.43.217.14, 202.43.217.15, 202.43.217.16 202.43.217.17, 202.165.102.111, 202.165.102.112, 202.165.102.113
> www.yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.yisou.com
Addresses: 202.43.217.17, 202.165.102.111, 202.165.102.112, 202.165.102.113 202.165.102.114, 202.43.217.14, 202.43.217.15, 202.43.217.16
> mp3.yisou.com
Server: UnKnown
Address: 192.168.1.254
Non-authoritative answer:
Name: www.yisou.com
Addresses: 202.165.102.113, 202.165.102.114, 202.43.217.14, 202.43.217.15 202.43.217.16, 202.43.217.17, 202.165.102.111, 22.165.102.112
Aliases: mp3.yisou.com
前臺做了8臺服務器的緩存集群，www.yisou.com和 yisou.com以及mp3.yisou.com是用的同一個集群。
通過前面的分析我們可以得到一個結論：sina和sohu使用了CDN與GSBL與DNS負載均衡技術，每個地區一組前臺服務器群，網易，百度使用了DNS負載均衡技術，每個頻道一組前臺服務器，一搜使用了DNS負載技術，所有頻道共用一組前臺服務器集群。
