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From Jason Venner <jason.had...@gmail.com>
Subject Re: About the memory file system, any suggestions?
Date Mon, 12 Oct 2009 15:46:35 GMT
You could use the jvm reuse features, and static objects will persist across
They will not persist across jobs.
In the prohadoop book example code, there is a jvm reuse example that
demonstrates this.

On Sun, Oct 11, 2009 at 10:37 PM, 曹楠楠 <michael.caoo@gmail.com> wrote:

> Hi all :
> I try to use the memory file system in hadoop. the idea is very simple. I
> want to use memory file system to  the map intermediate file. It is like
> this; 1. the memory is limited, the data will be written into the disk.
> 2.If
> the file in memory is deleted and there are space in memory, the data will
> be prefetched by a thread into the memory.3.If the data is not in memory,
> then read it directly from disk.
> But when I try to implement it in hadoop. I find that when the tasktracker
> receive a new map or reduce task, it will start a new process. If I use the
> memory file system, the intermediate file will be written into map task
> process address space. And task tracker can't access to it. So any
> suggestions?
> Thanks a lot :)

Pro Hadoop, a book to guide you from beginner to hadoop mastery,
www.prohadoopbook.com a community for Hadoop Professionals

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