名称节点在哪里存储fsImage并编辑日志？ [英] Where does Name node store fsImage and edit Log?

问题描述

我是一名java程序员，学习Hadoop。
我读到HDFS中的Name节点将其信息存储到两个文件中，即fsImage& Editlog的。在启动的情况下，它从磁盘和磁盘读取这些数据。执行检查点操作。

但是在许多地方，我还读到Name Node将数据存储在RAM&这就是为什么apache建议为名称节点服务器使用高内存的机器。

请在此指导我。
它将什么数据存储在RAM和RAM中？

对不起，如果我问任何明显的问题。

解决方案

让我先回答

它将什么数据存储在RAM&它在哪里存储fsImage和编辑日志？

在RAM中 - 文件阻塞和阻塞到数据节点映射。
在持久性存储中（包括编辑日志和fsimage） - 与文件相关的元数据（权限，名称等）

关于fsimage的存储位置和editlog @ mashuai的答案是现货。

有关更详细的讨论，您可以阅读此

I am a java programmer, learning Hadoop. I read that the Name node in HDFS stores its information into two files namely fsImage & editLog. In case of start up it reads this data from the disk & performs checkpoint operation.

But at many places I also read that Name Node stores the data in RAM & that is why apache recommends a machine with high RAM for Name Node server.

Please enlighten me on this. What data does it store in RAM & where does it store fsImage and edit Log ?

Sorry if I asked anything obvious.

解决方案

Let me first answer

What data does it store in RAM & where does it store fsImage and edit Log ?

In RAM -- file to block and block to data node mapping. In persistent storage (includes both edit log and fsimage) -- file related metadata (permissions, name and so on)

Regarding the storage location of the fsimage and editlog @mashuai's answer is spot on.

For a more detailed discussion you can read up on this

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