在HDFS的FsImage内容 [英] Content of the fsimage hdfs

问题描述

我对什么是在所有的FsImage对元数据的问题。我读了所有突变对文件系统命名空间，如文件重命名，权限更改，文件创建，块分配是里面的FsImage。但是，块位置的数据呢？
是否包含在哪里（上数据节点）的块存储的信息，以及？
的http：// bradhedlund我从这个来源得到的。 COM / 2011/09/10 /理解-的Hadoop集群和-的网络/ 中，关于块存储的位置元数据是由数据节点的块repots建设。
这是真的？所以的FsImage不包含有关块位置的信息？

I have a question on what is the metadata in the fsimage all about. I read that All mutations to the file system namespace, such as file renames, permission changes, file creations, block allocations are inside the fsimage. But the block location data as well? Does it contain the information about where (on which datanode) the blocks are stores as well? I get from this source: http://bradhedlund.com/2011/09/10/understanding-hadoop-clusters-and-the-network/ that the metadata on where blocks is stored is build by the block repots of the datanodes. Is this true? So the Fsimage does not contain information about the block locations?

推荐答案

的Namenode维护两个类型的数据。

Namenode maintains two type of data

阻止位置数据：由于文件被切成块，NN应该知道哪一块是哪里。
该数据保存在内存和从不坚持在磁盘上，DNS谈话NN定期和分享blockreport。

Block Location data : Since files are chopped into blocks, NN should know which piece is where. This data is kept in memory and never persisted on disk, DNs talk to NN periodically and share the blockreport.

文件系统（元数据）：如文件系统层次，权限等，这是信息保存到磁盘

file system (metadata) : such as the file system hierarchy, permissions, etc. This info is persisted to the disk

的FsImage 并从应用编辑日志的编辑到它，这个过程后，我们得到一个新的快照。从这个角度上的NameNode可以接受的文件来自客户端系统的请求/ DNS

when namenodes starts up it loads "snapshot" of filesystem from fsimage and applies the edit logs from edits onto it, after this process we get a new snapshot. from this point on namenode can accept files system requests from clients / DNs

这篇关于在HDFS的FsImage内容的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！