Terracotta Discussion Forums (LEGACY READ-ONLY ARCHIVE)

请问Terracotta技术对集群节点的数目有没有限制？如果要搭建几百台服务器的集群，会不会造成网络阻塞，导致集群的负载能力严重下降？

谢谢！

这个问题问得比较“大”，也是很多使用Terracotta的朋友关心的问题。
官方的回答是：要根据你的的应用的特点来看。没有标准答案。
不过在Terracotta自己的实验室里面，我们曾经搭建过400台JVM和一台DSO服务器的环境，运行很简单的应用。整个运行效果还不错。在客户的生产环境也有超过100台JVM的集群。
由于Terracotta使用TCP/IP点对点协议，而不是UDP广播，因此对网络的负载是线性增长的。几百个TCP/IP连接对于现在的网络设备来说根本不成问题。

现在回到官方的答案：
如果您的应用能够做到很好的locality(本地化)，或者说能够把各个节点处理的数据区分的很明确，就会大大减少锁冲突和数据同步带来的资源竞争和网络负载。
另外对于共享数据的读写比例也是对性能影响很大的关键指标。一般来讲如果能保证90/10的读写比率，对性能的影响会比较小。因为写数据的时候，整个集群内要做到数据同步，开销会非常大。

因此要想知道Terracotta到底能支持多少节点，真的需要根据用户自身应用的特点，进行大量的测试、优化，才能得到最终的答案。

Terracotta大大简化了Java集群的构建，但是这里面没有Magic。能否构建出最好的Java集群，还是要看系统架构师的功力。

Sorry I don't speak Chinese so I cannot answer in kind--wish I could :(

Anyways, I would add to Lima's response and suggest you look at Terracotta FX server arrays. As your cluster gets larger, we just add more Terracotta servers to the array.

Watch this video: http://www.terracotta.org/attach/qt/terracotta_3.0/terracotta_3.0_server_striping.html

Also, I can share performance testing numbers in Amazon EC2. These are unofficial, but so far we have run a web application on Tomcat with HTTP session objects of about 1KB each, 50% of all requests doing updates. We were able to handle 36 Tomcat instances talking to 1 Terracotta Server before the server was exhausted. We then reran the test with 2 Terracotta Servers working as an array and got to 72 JVMs before exhausting both servers. perfectly linear scale (at least to that level). And the partitioning is done inside our product--transparent to your application.

Hope this helps.

--Ari

What's tps on 36 client + 1 server cluster?
what's tps on 72 client + 2 server cluster?

I think the Terracotta server was seeing 7K tps. The Tomcat instances were each doing more.

So 14K tps w/ 2 Terracotta servers...

--Ari