twitter.com网站又挂了

因为网站的流量实在太大，而twitter的缓存策略设置的不合理，今天twitter网站又挂掉了。twitter的开发人员在博客上面写到：

引用

ht now, Twitter is suffering slowdowns. Earlier today it was down again.

There are an excessive number of single points of failure in the current system, and through developer error* and external circumstance we have managed to hit quite a few of them in the last week. I am sorry and embarrassed.

In particular, we mis-estimated the impact of some cache policy changes. If your site runs so hot that it can't function without memcached, you'd better understand exactly how much buffer capacity you actually have.

We're working on fixing it all, but it takes a long time...

系统当中出现了太多的单点失败，我们错误的估计了缓存策略修改以后带来的影响，如果你的热门网站无法从memcached当中获益，那么你最好准确的估算系统的实际缓存能力。