CODEWITHSUNDEEP
hadoophdfs
drecute
drecute

Reputation: 758

Hadoop replication factor precedence

I have this only in my namenode:

<property>
  <name>dfs.replication</name>
  <value>3</value>
</property>

In my data nodes, I have this:

<property>
  <name>dfs.replication</name>
  <value>1</value>
</property>

Now my question is, will the replication factor be 3 or 1?

At the moment, the output of hdfs dfs -ls hdfs:///user/hadoop-user/data/0/0/0 shows 1 replication factor:

-rw-r--r--   1 hadoop-user supergroup      68313 2015-11-06 19:32 hdfs:///user/hadoop-user/data/0/0/0/00099954tnemhcatta.bin

Appreciate your answer.

Upvotes: 0

Views: 172

Answers (2)

Kishore
Kishore

Reputation: 5891

by default replication factor is 3, it is standard in most of the distributed system. if the replication factor was set to 3 (default value in HDFS) there would be one original block and two replicas. Most of time when we working on single node cluster(single machine) that time we put it 1. because if we will take 3 then there will be no benefit as all the copy are on single machine. so simple understanding. in multi node cluster replication factor should be 3 used in failure and in single machine replication factor should be 1.

Upvotes: 2

JYOTI RANJAN PANDA
JYOTI RANJAN PANDA

Reputation: 122

Open the hdfs-site.xml file. This file is usually found in the conf/ folder of the Hadoop installation directory. Change or add the following property to hdfs-site.xml:

<property> 
<name>dfs.replication<name> 
<value>3<value> 
<description>Block Replication<description> 
<property>

You can also change the replication factor on a per-file basis using the Hadoop FS shell.

[jpanda@localhost ~]$ hadoop fs –setrep –w 3 /my/file

Alternatively, you can change the replication factor of all the files under a directory.

[jpanda@localhost ~]$ hadoop fs –setrep –w 3 -R /my/dir

Upvotes: 0

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