question Re: Unable to change the replication factor from 3 to 2 in Archives of Support Questions (Read Only)

Unable to change the replication factor from 3 to 2

Learner_1122 — Tue, 05 Dec 2017 20:26:09 GMT

Hi Guys,
I have been trying to change the replication factor from "3" to "2". but failed.
Here the steps :
1. First I check the replication factor from Ambari server. it is "3".
2. Then i go to shell and check the replication factor by wrote the commands :
"cd /etc/hadoop/conf" :

"View hdfs-site.xml"
replication factor is "3" also here.
3. Then i go to Ambari server and Change the replication factor from "3" to "2" and final it by click the "Lock" button and then Save.
4. and then i have restart the all services.
after these steps Ambari server show me replication factor "2" . BUT when i go to shell and write the command :
"View hdfs-site.xml"
it show me replication factor still "3" .
What thing i did wrong ?
Thanks

Re: Unable to change the replication factor from 3 to 2

erkansirin78 — Tue, 05 Dec 2017 21:24:01 GMT

Hi @Mudassar Hussain

Did you put namenode safemode and save the namespace?

sudo su hdfs -l -c 'hdfs dfsadmin -safemode enter'
sudo su hdfs -l -c 'hdfs dfsadmin -saveNamespace'

restart sevices and see hdfs-site.xml

cat /etc/hadoop/conf/hdfs-site.xml
<property>
 <name>dfs.replication</name>
 <value>2</value>
</property>

You can also check that Ambari Dashboard HDFS Disk Usage is decreased.

Re: Unable to change the replication factor from 3 to 2

Learner_1122 — Sun, 18 Aug 2019 02:44:16 GMT

Thanks @Erkan ŞİRİN
when i write the above command it give me an error. Please see the image :

and is it right that Replication-Factor change effect apply on new file not on old file ?

Re: Unable to change the replication factor from 3 to 2

erkansirin78 — Thu, 07 Dec 2017 00:29:00 GMT

Hi, please give the command with root user.

[root@namenode~]# sudo su hdfs -l -c 'hdfs dfsadmin -safemode enter'
[root@namenode~]# sudo su hdfs -l -c 'hdfs dfsadmin -saveNamespace'

Re: Unable to change the replication factor from 3 to 2

Learner_1122 — Thu, 07 Dec 2017 15:53:24 GMT

Thanks a lot @Erkan ŞİRİN this works 🙂
Now how i put the @NameNode into "Normal Mode" ?
and what the reason to put the @namenode in safeMode ?

Re: Unable to change the replication factor from 3 to 2

Learner_1122 — Thu, 07 Dec 2017 15:55:14 GMT

Thanks a lot @Erkan ŞİRİN it works 🙂 How i put the @namenode into normal mode ? and what is the reason to put the @namenode into safe mode ?

Re: Unable to change the replication factor from 3 to 2

erkansirin78 — Thu, 07 Dec 2017 21:44:17 GMT

It is because the way how namenode works. It merges namespace repo (fsimage) periodically with edit logs file. To prevent namespace inconsistency it stops changing namespace by entering safemode.

hdfs dfsadmin -safemode leave

should work.