Masters — HDFS NameNode, YARN ResourceManager, and HBase Master.
Slaves — HDFS DataNodes, YARN NodeManagers, and HBase RegionServers.
slave 节点的机器配置建议
机柜: 1U or 2U 都可以。具体看机器配置 一个机柜一般可以存放19个机架


如何查看CMS 的gc日志

最近在重新整理JVM方面的知识,看到很久以前的一篇对于CMS GC解读的日志,这篇博客地址是 https://blogs.oracle.com/poonam/entry/understanding_cms_gc_logs 。现在看来还是很有收获,就决定放出来。
CMS GC with -XX:+PrintGCDetails and -XX:+PrintGCTimeStamps prints a lot of information. Understanding this information can help in fine tuning various parameters of the application and CMS to achieve best performance.
Let’s have a look at some of the CMS logs generated with 1.4.2_10:
39.910: [GC 39.910: [ParNew: 261760K->0K(261952K), 0.2314667 secs] 262017K->26386K(1048384K), 0.2318679 secs]
Young generation (ParNew) collection. Young generation capacity is 261952K and after the collection its occupancy drops down from 261760K to 0. This collection took 0.2318679 secs.
## 新生代GC,新生代大小是262017K,一次GC,新生代从261760K降到了0K。花费了0.2318679 s


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