What are the HDFS configuration parameters in CentOS

The configuration of Hadoop distributed file system (HDFS) in CentOS system mainly relies on two configuration files: hdfs-site.xml and core-site.xml . This article will introduce some key HDFS configuration parameters and their functions.

hdfs-site.xml configuration parameters detailed explanation

The following parameters are common configuration items in the hdfs-site.xml file, which are critical to HDFS performance and reliability:

• dfs.replication : Defines the number of copies of the data block. The default value is 3, but should be adjusted according to cluster size and fault tolerance requirements. The more copies, the higher the data security, but the greater the storage space.

• dfs.namenode.http-address : Specifies the HTTP service address and port number of NameNode to access NameNode's Web UI.

• dfs.namenode.name.dir : Sets the storage path of NameNode metadata. This path must exist and has the correct permissions.

• dfs.datanode.data.dir : Specifies the directory where DataNode stores data blocks. Multiple directories can be configured to improve data distribution and availability.

• dfs.block.size : Defines the size of the data block, the default is 128MB. Adjusting this parameter requires a trade-off between network transmission efficiency and disk addressing time.

• dfs.namenode.handler.count : Configure the number of threads that NameNode can handle RPC requests. Increasing the number of threads can improve the concurrent processing capability of NameNode.

• dfs.datanode.handler.count : Configures the number of threads that DataNode handles RPC requests. Similar to NameNode, it is used to improve the concurrent processing capability of DataNode.

• dfs.datanode.max.xcievers : Limits the number of data transmission connections that DataNode processes simultaneously.

• dfs.permissions : Controls whether file permission checking is enabled, default is true .

• dfs.datanode.du.reserved : Sets the size of reserved space that HDFS cannot use on each volume to prevent insufficient disk space from causing system failure.

• dfs.datanode.failed.volumes.tolerated : Specifies the number of corrupt data volumes that DataNode can tolerate.

Detailed explanation of core-site.xml configuration parameters

The core-site.xml file contains some core configuration parameters of Hadoop, among which HDFS-related parameters include:

• fs.defaultFS : Defines the default file system URI of HDFS, which usually points to the address and port number of NameNode, for example: hdfs://namenode-host:9000 .

• fs.checkpoint.dir : Specifies the directory where SecondaryNameNode stores the checkpoint image file. SecondaryNameNode is used to regularly backup NameNode's metadata to improve HDFS availability.

• hadoop.tmp.dir : Sets the storage directory for Hadoop temporary files.

Important tip : The above parameters are only part of the HDFS configuration, and the actual configuration needs to be adjusted according to the cluster size, hardware resources and business needs. Before modifying the configuration file, it is recommended to back up the original file and carefully read the official Hadoop document to ensure the correctness of the configuration. Incorrect configuration can cause HDFS to run abnormally or even data loss.

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