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Archive for April 2012

jmap-jmap是java自带的jvm内存工具,可以通过在服务器执行:jmap -dump:format=b,file=heap.bin pid 将jvm内存dump到一个文件里。
这里可以通过jhat-也是一个java自带的内存分析工具 ,来分析dump出来的heap.bin,它会启动一个7000端口的服务,你可以在浏览器访问这个端口,获取堆栈信息;命令: jhat -J-Xmx512m heap.bin
另外一个工具就是mat:http://www.eclipse.org/mat/ 可以在eclipse上安装这个插件,通过eclipse打开这个文件就可以分析jvm的内存情况。如下图:
另外一个分析jvm中native stack的分析工具是google的perftools,这个没有深入研究,先mark一下。
分析jvm行为的工具,btrace,可以通过编写源码的方式来观察jvm中方法调用等一些行为。

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Posted on: April 9, 2012

Highly Scalable Blog

NoSQL databases are often compared by various non-functional criteria, such as scalability, performance, and consistency. This aspect of NoSQL is well-studied both in practice and theory because specific non-functional properties are often the main justification for NoSQL usage and fundamental results on distributed systems like the CAP theorem apply well to NoSQL systems.  At the same time, NoSQL data modeling is not so well studied and lacks the systematic theory found in relational databases. In this article I provide a short comparison of NoSQL system families from the data modeling point of view and digest several common modeling techniques.

I would like to thank Daniel Kirkdorffer who reviewed the article and cleaned up the grammar.

To  explore data modeling techniques, we have to start with a more or less systematic view of NoSQL data models that preferably reveals trends and interconnections. The following figure depicts imaginary “evolution” of the major NoSQL…

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