Merging change r1186579 for HDFS-2471 from 0.23 branch
git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1186584 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Suresh Srinivas
parent
aeae1ba497
commit
37137845c8
@ -832,6 +832,8 @@ Release 0.23.0 - Unreleased
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HDFS-2401. Running a set of methods in a Single Test Class.
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(Jonathan Eagles via mahadev)
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HDFS-2471. Add federation documentation. (suresh)
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OPTIMIZATIONS
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HDFS-1458. Improve checkpoint performance by avoiding unnecessary image
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@ -394,19 +394,19 @@ Hadoop MapReduce Next Generation - Cluster Setup
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Format a new distributed filesystem:
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----
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$ $HADOOP_HDFS_HOME/bin/hdfs namenode -format <cluster_name>
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$ $HADOOP_PREFIX_HOME/bin/hdfs namenode -format <cluster_name>
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----
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Start the HDFS with the following command, run on the designated NameNode:
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----
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$ $HADOOP_HDFS_HOME/bin/hdfs start namenode --config $HADOOP_CONF_DIR
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$ $HADOOP_PREFIX_HOME/bin/hdfs start namenode --config $HADOOP_CONF_DIR
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----
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Run a script to start DataNodes on all slaves:
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----
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$ $HADOOP_HDFS_HOME/bin/hdfs start datanode --config $HADOOP_CONF_DIR
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$ $HADOOP_PREFIX_HOME/bin/hdfs start datanode --config $HADOOP_CONF_DIR
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----
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Start the YARN with the following command, run on the designated
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@ -435,13 +435,13 @@ Hadoop MapReduce Next Generation - Cluster Setup
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NameNode:
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----
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$ $HADOOP_HDFS_HOME/bin/hdfs stop namenode --config $HADOOP_CONF_DIR
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$ $HADOOP_PREFIX_HOME/bin/hdfs stop namenode --config $HADOOP_CONF_DIR
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----
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Run a script to stop DataNodes on all slaves:
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----
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$ $HADOOP_HDFS_HOME/bin/hdfs stop datanode --config $HADOOP_CONF_DIR
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$ $HADOOP_PREFIX_HOME/bin/hdfs stop datanode --config $HADOOP_CONF_DIR
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----
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Stop the ResourceManager with the following command, run on the designated
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@ -910,21 +910,21 @@ KVNO Timestamp Principal
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Format a new distributed filesystem as <hdfs>:
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----
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[hdfs]$ $HADOOP_HDFS_HOME/bin/hdfs namenode -format <cluster_name>
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[hdfs]$ $HADOOP_PREFIX_HOME/bin/hdfs namenode -format <cluster_name>
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----
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Start the HDFS with the following command, run on the designated NameNode
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as <hdfs>:
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----
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[hdfs]$ $HADOOP_HDFS_HOME/bin/hdfs start namenode --config $HADOOP_CONF_DIR
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[hdfs]$ $HADOOP_PREFIX_HOME/bin/hdfs start namenode --config $HADOOP_CONF_DIR
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----
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Run a script to start DataNodes on all slaves as <root> with a special
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environment variable <<<HADOOP_SECURE_DN_USER>>> set to <hdfs>:
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----
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[root]$ HADOOP_SECURE_DN_USER=hdfs $HADOOP_HDFS_HOME/bin/hdfs start datanode --config $HADOOP_CONF_DIR
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[root]$ HADOOP_SECURE_DN_USER=hdfs $HADOOP_PREFIX_HOME/bin/hdfs start datanode --config $HADOOP_CONF_DIR
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----
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Start the YARN with the following command, run on the designated
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@ -953,13 +953,13 @@ KVNO Timestamp Principal
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as <hdfs>:
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----
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[hdfs]$ $HADOOP_HDFS_HOME/bin/hdfs stop namenode --config $HADOOP_CONF_DIR
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[hdfs]$ $HADOOP_PREFIX_HOME/bin/hdfs stop namenode --config $HADOOP_CONF_DIR
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----
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Run a script to stop DataNodes on all slaves as <root>:
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----
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[root]$ $HADOOP_HDFS_HOME/bin/hdfs stop datanode --config $HADOOP_CONF_DIR
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[root]$ $HADOOP_PREFIX_HOME/bin/hdfs stop datanode --config $HADOOP_CONF_DIR
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----
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Stop the ResourceManager with the following command, run on the designated
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@ -998,4 +998,4 @@ KVNO Timestamp Principal
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| | | Default HTTP port is 19888. |
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*-------------------------+-------------------------+------------------------+
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@ -0,0 +1,343 @@
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~~ Licensed under the Apache License, Version 2.0 (the "License");
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~~ you may not use this file except in compliance with the License.
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~~ You may obtain a copy of the License at
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~~
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~~ http://www.apache.org/licenses/LICENSE-2.0
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~~
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~~ Unless required by applicable law or agreed to in writing, software
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~~ distributed under the License is distributed on an "AS IS" BASIS,
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~~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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~~ See the License for the specific language governing permissions and
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~~ limitations under the License. See accompanying LICENSE file.
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---
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Hadoop Map Reduce Next Generation-${project.version} - Cluster Setup
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---
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---
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${maven.build.timestamp}
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HDFS Federation
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\[ {{{./index.html}Go Back}} \]
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%{toc|section=1|fromDepth=0}
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This guide provides an overview of the HDFS Federation feature and
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how to configure and manage the federated cluster.
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* {Background}
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[./federation-background.gif] HDFS Layers
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HDFS has two main layers:
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* <<Namespace>>
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* Consists of directories, files and blocks
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* It supports all the namespace related file system operations such as
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create, delete, modify and list files and directories.
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* <<Block Storage Service>> has two parts
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* Block Management (which is done in Namenode)
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* Provides datanode cluster membership by handling registrations, and
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periodic heart beats.
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* Processes block reports and maintains location of blocks.
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* Supports block related operations such as create, delete, modify and
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get block location.
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* Manages replica placement and replication of a block for under
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replicated blocks and deletes blocks that are over replicated.
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* Storage - is provided by datanodes by storing blocks on the local file
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system and allows read/write access.
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The current HDFS architecture allows only a single namespace for the
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entire cluster. A single Namenode manages this namespace. HDFS
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Federation addresses limitation of current architecture by adding
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support multiple Namenodes/namespaces to HDFS file system.
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* {HDFS Federation}
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In order to scale the name service horizontally, federation uses multiple
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independent Namenodes/namespaces. The Namenodes are federated, that is, the
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Namenodes are independent and don’t require coordination with each other.
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The datanodes are used as common storage for blocks by all the Namenodes.
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Each datanode registers with all the Namenodes in the cluster. Datanodes
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send periodic heartbeats and block reports and handles commands from the
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Namenodes.
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[./federation.gif] HDFS Federation Architecture
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<<Block Pool>>
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A Block Pool is a set of blocks that belong to a single namespace.
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Datanodes store blocks for all the block pools in the cluster.
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It is managed independently of other block pools. This allows a namespace
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to generate Block IDs for new blocks without the need for coordination
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with the other namespaces. The failure of a Namenode does not prevent
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the datanode from serving other Namenodes in the cluster.
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A Namespace and its block pool together are called Namespace Volume.
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It is a self-contained unit of management. When a Namenode/namespace
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is deleted, the corresponding block pool at the datanodes is deleted.
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Each namespace volume is upgraded as a unit, during cluster upgrade.
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<<ClusterID>>
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A new identifier <<ClusterID>> is added to identify all the nodes in
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the cluster. When a Namenode is formatted, this identifier is provided
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or auto generated. This ID should be used for formatting the other
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Namenodes into the cluster.
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** Key Benefits
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* Namespace Scalability - HDFS cluster storage scales horizontally but
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the namespace does not. Large deployments or deployments using lot
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of small files benefit from scaling the namespace by adding more
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Namenodes to the cluster
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* Performance - File system operation throughput is currently limited
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by a single Namenode. Adding more Namenodes to the cluster scales the
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file system read/write operations throughput.
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* Isolation - A single Namenode offers no isolation in multi user
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environment. An experimental application can overload the Namenode
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and slow down production critical applications. With multiple Namenodes,
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different categories of applications and users can be isolated to
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different namespaces.
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* {Federation Configuration}
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Federation configuration is <<backward compatible>> and allows existing
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single Namenode configuration to work without any change. The new
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configuration is designed such that all the nodes in the cluster have
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same configuration without the need for deploying different configuration
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based on the type of the node in the cluster.
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A new abstraction called <<<NameServiceID>>> is added with
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federation. The Namenode and its corresponding secondary/backup/checkpointer
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nodes belong to this. To support single configuration file, the Namenode and
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secondary/backup/checkpointer configuration parameters are suffixed with
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<<<NameServiceID>>> and are added to the same configuration file.
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** Configuration:
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<<Step 1>>: Add the following parameters to your configuration:
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<<<dfs.federation.nameservices>>>: Configure with list of comma separated
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NameServiceIDs. This will be used by Datanodes to determine all the
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Namenodes in the cluster.
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<<Step 2>>: For each Namenode and Secondary Namenode/BackupNode/Checkpointer
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add the following configuration suffixed with the corresponding
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<<<NameServiceID>>> into the common configuration file.
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*---------------------+--------------------------------------------+
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|| Daemon || Configuration Parameter |
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*---------------------+--------------------------------------------+
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| Namenode | <<<dfs.namenode.rpc-address>>> |
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| | <<<dfs.namenode.servicerpc-address>>> |
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| | <<<dfs.namenode.http-address>>> |
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| | <<<dfs.namenode.https-address>>> |
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| | <<<dfs.namenode.keytab.file>>> |
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| | <<<dfs.namenode.name.dir>>> |
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| | <<<dfs.namenode.edits.dir>>> |
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| | <<<dfs.namenode.checkpoint.dir>>> |
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| | <<<dfs.namenode.checkpoint.edits.dir>>> |
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*---------------------+--------------------------------------------+
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| Secondary Namenode | <<<dfs.namenode.secondary.http-address>>> |
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| | <<<dfs.secondary.namenode.keytab.file>>> |
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*---------------------+--------------------------------------------+
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| BackupNode | <<<dfs.namenode.backup.address>>> |
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| | <<<dfs.secondary.namenode.keytab.file>>> |
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*---------------------+--------------------------------------------+
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Here is an example configuration with two namenodes:
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----
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<configuration>
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<property>
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<name>dfs.federation.nameservices</name>
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<value>ns1,ns2</value>
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</property>
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<property>
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<name>dfs.namenode.rpc-address.ns1</name>
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<value>hdfs://nn-host1:rpc-port</value>
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</property>
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<property>
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<name>dfs.namenode.http-address.ns1</name>
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<value>nn-host1:http-port</value>
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</property>
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<property>
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<name>dfs.namenode.secondaryhttp-address.ns1</name>
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<value>snn-host1:http-port</value>
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</property>
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<property>
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<name>dfs.namenode.rpc-address.ns2</name>
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<value>hdfs://nn-host2:rpc-port</value>
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</property>
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<property>
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<name>dfs.namenode.http-address.ns2</name>
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<value>nn-host2:http-port</value>
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</property>
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<property>
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<name>dfs.namenode.secondaryhttp-address.ns2</name>
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<value>snn-host2:http-port</value>
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</property>
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.... Other common configuration ...
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</configuration>
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----
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** Formatting Namenodes
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<<Step 1>>: Format a namenode using the following command:
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----
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> $HADOOP_PREFIX_HOME/bin/hdfs namenode -format [-clusterId <cluster_id>]
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----
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Choose a unique cluster_id, which will not conflict other clusters in
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your environment. If it is not provided, then a unique ClusterID is
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auto generated.
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<<Step 2>>: Format additional namenode using the following command:
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----
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> $HADOOP_PREFIX_HOME/bin/hdfs namenode -format -clusterId <cluster_id>
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----
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Note that the cluster_id in step 2 must be same as that of the
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cluster_id in step 1. If they are different, the additional Namenodes
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will not be part of the federated cluster.
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** Upgrading from older release to 0.23 and configuring federation
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Older releases supported a single Namenode. Here are the steps enable
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federation:
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Step 1: Upgrade the cluster to newer release. During upgrade you can
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provide a ClusterID as follows:
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----
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> $HADOOP_PREFIX_HOME/bin/hdfs start namenode --config $HADOOP_CONF_DIR -upgrade -clusterId <cluster_ID>
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----
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If ClusterID is not provided, it is auto generated.
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** Adding a new Namenode to an existing HDFS cluster
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Follow the following steps:
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* Add configuration parameter <<<dfs.federation.nameservices>>> to
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the configuration.
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* Update the configuration with NameServiceID suffix. Configuration
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key names have changed post release 0.20. You must use new configuration
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parameter names, for federation.
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* Add new Namenode related config to the configuration files.
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* Propagate the configuration file to the all the nodes in the cluster.
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* Start the new Namenode, Secondary/Backup.
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* Refresh the datanodes to pickup the newly added Namenode by running
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the following command:
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----
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> $HADOOP_PREFIX_HOME/bin/hdfs dfadmin -refreshNameNode <datanode_host_name>:<datanode_rpc_port>
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----
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* The above command must be run against all the datanodes in the cluster.
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* {Managing the cluster}
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** Starting and stopping cluster
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To start the cluster run the following command:
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----
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> $HADOOP_PREFIX_HOME/bin/start-dfs.sh
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----
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To start the cluster run the following command:
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----
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> $HADOOP_PREFIX_HOME/bin/stop-dfs.sh
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----
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These commands can be run from any node where the HDFS configuration is
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available. The command uses configuration to determine the Namenodes
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in the cluster and starts the Namenode process on those nodes. The
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datanodes are started on nodes specified in the <<<slaves>>> file. The
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script can be used as reference for building your own scripts for
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starting and stopping the cluster.
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** Balancer
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Balancer has been changed to work with multiple Namenodes in the cluster to
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balance the cluster. Balancer can be run using the command:
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----
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"$HADOOP_PREFIX"/bin/hadoop-daemon.sh --config $HADOOP_CONF_DIR --script "$bin"/hdfs start balancer [-policy <policy>]
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----
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Policy could be:
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* <<<node>>> - this is the <default> policy. This balances the storage at
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the datanode level. This is similar to balancing policy from prior releases.
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* <<<blockpool>>> - this balances the storage at the block pool level.
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Balancing at block pool level balances storage at the datanode level also.
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Note that Balander only balances the data and does not balance the namespace.
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** Decommissioning
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Decommissioning is similar to prior releases. The nodes that need to be
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decommissioning are added to the exclude file at all the Namenode. Each
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Namenode decommissions its Block Pool. When all the Namenodes finish
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decommissioning a datanode, the datanode is considered to be decommissioned.
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<<Step 1>>: To distributed an exclude file to all the Namenodes, use the
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following command:
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----
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"$HADOOP_PREFIX"/bin/distributed-exclude.sh <exclude_file>
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----
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<<Step 2>>: Refresh all the Namenodes to pick up the new exclude file.
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----
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"$HADOOP_PREFIX"/bin/refresh-namenodes.sh
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----
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The above command uses HDFS configuration to determine the Namenodes
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configured in the cluster and refreshes all the Namenodes to pick up
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the new exclude file.
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** Cluster Web Console
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Similar to Namenode status web page, a Cluster Web Console is added in
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federation to monitor the federated cluster at
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<<<http://<any_nn_host:port>/dfsclusterhealth.jsp>>>.
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Any Namenode in the cluster can be used to access this web page.
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The web page provides the following information:
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* Cluster summary that shows number of files, number of blocks and
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total configured storage capacity, available and used storage information
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for the entire cluster.
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* Provides list of Namenodes and summary that includes number of files,
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blocks, missing blocks, number of live and dead data nodes for each
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Namenode. It also provides a link to conveniently access Namenode web UI.
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* It also provides decommissioning status of datanodes.
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@ -49,3 +49,5 @@ Hadoop MapReduce Next Generation
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|
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* {{{./CapacityScheduler.html}Capacity Scheduler}}
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* {{{./Federation.html}HDFS Federation feature description, configuration and management}}
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