上午11:23左右,在公司无法访问百度,开始我还怀疑是公司网络(网通线路)的问题,后来在BBS上看到还有其他地区的网通用户也都无法访问百度。

  后来获知,百度服务器托管的中国网通土城IDC机房发生故障,百度的网通服务器全部无法访问。托管在该机房的大型网站还有搜狐、TOM、九城。我用Linux的dig命令查询出百度的网通IP──202.108.22.5、202.108.22.43,直接访问IP也无法打开:
引用
[root@zhangyan4 zhangyan4]# dig www.baidu.com
;; ANSWER SECTION:
www.baidu.com.          84      IN      CNAME   www.a.shifen.com.
www.a.shifen.com.       303     IN      A       202.108.22.5
www.a.shifen.com.       303     IN      A       202.108.22.43

  20多分钟后,百度恢复正常。我再次dig一下www.baidu.com,发现域名已经解析到220.181.37.4、220.181.38.4这两个电信的IP上:
引用
[root@zhangyan4 zhangyan4]# dig www.baidu.com
;; ANSWER SECTION:
www.baidu.com.          129     IN      CNAME   www.a.shifen.com.
www.a.shifen.com.       356     IN      A       220.181.37.4
www.a.shifen.com.       356     IN      A       220.181.38.4


  百度在DNS服务器更改域名A记录后,几分钟后理应可以生效。但是域名的TTL记录设置了缓存的时间,在这个时间内,如果需要重新解析域名,会直接从用户本地的缓存读取,而不是直接向DNS服务器请求。这样就导致了在百度网通机房发生故障的那段时间内,访问过百度的网通用户在百度切换域名后的一段时间内仍然无法访问。

  上周,我部署过一组的服务器,可以像百度一样进行电信、网通线路互相切换的容灾处理。但电信切到网通,网通切到电信,必将导致其中一方用户的访问速度变慢,所以只是解决故障的权宜之计。等我们部门本季度的服务器采购到位后,我们将部署北京电信与外地电信,北京网通与外地网通之间的冗余互备。
  点击在新窗口中浏览此图片


电脑杂谈 | 评论(36) | 引用(0) | 阅读(28228)
民大学弟
2007-7-18 22:49
看来张宴大哥不仅精通PHP,计算机网络、Linux也学得不赖嘛……如果在工作和学习中有什么感想和经验的话,尽管发帖子哈!呵呵,我会一直顶你、一直关注你的博客的……
jackbillow
2007-9-5 08:58
问一下张兄,上面图上的专线,是怎么实现的?
张宴 回复于 2007-9-6 13:14
sina自己埋设了一条10GB光缆,将电信和网通的IDC机房连接起来。
jackbillow Email
2007-9-5 09:00
有空了,能不能把sina的部署的结构图大致画一下。想看看sina的结构。
我们用了两台以斯列的设备:crescendo.。
张宴 回复于 2007-9-6 13:03
对不起,这是机密信息,不能提供。
johnzw
2007-9-7 14:45
sina的域名不用f5的3-DNS做负载?
lixulong Email
2008-3-28 14:14
嘿嘿`,  不错,我喜欢
hery Homepage
2008-12-6 11:37
grin强悍,自己用过光纤把电信和网通的机房连接起来,这样以来就变成双线了哈,这个主意好
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