Your cluster implements HDFS High Availability (HA). Your two NameNodes are named nn01 and
nn02. What occurs when you execute the command: hdfs haadmin –failover nn01 nn02?
A.
nn02 is fenced, and nn01 becomes the active NameNode
B.
nn01 is fenced, and nn02 becomes the active NameNode
C.
nn01 becomes the standby NameNode and nn02 becomes the active NameNode
D.
nn02 becomes the standby NameNode and nn01 becomes the active NameNode
Explanation:
failover – initiate a failover between two NameNodes
This subcommand causes a failover from the first provided NameNode to the second. If the first
NameNode is in the Standby state, this command simply transitions the second to the Active state
without error. If the first NameNode is in the Active state, an attempt will be made to gracefullytransition it to the Standby state. If this fails, the fencing methods (as configured by
dfs.ha.fencing.methods) will be attempted in order until one of the methods succeeds. Only after
this process will the second NameNode be transitioned to the Active state. If no fencing method
succeeds, the second NameNode will not be transitioned to the Active state, and an error will be
returned.
As per my failover test Answer is “C”
0
0
Confuse with B and C
failover – initiate a failover between two NameNodes
This subcommand causes a failover from the first provided NameNode to the second. If the first NameNode is in the Standby state, this command simply transitions the second to the Active state without error. If the first NameNode is in the Active state, an attempt will be made to gracefully transition it to the Standby state. If this fails, the fencing methods (as configured by dfs.ha.fencing.methods) will be attempted in order until one succeeds. Only after this process will the second NameNode be transitioned to the Active state. If no fencing method succeeds, the second NameNode will not be transitioned to the Active state, and an error will be returned.
0
0
Correct answer is C.
B is not acceptable as the first Name-node could become stand-by without fencing.
0
0
Answer C is correct as this is graceful failover.
0
0
C
0
0
From document “Haddoop Operations”
…
If you have not configured automatic failover, you can manually activate the primary
namenode by running the command:
[root@hadoop-ha01 ~]# sudo -u hdfs hdfs haadmin -failover hadoop-ha02 hadoop-ha01
Failover to NameNode at hadoop-ha01/10.20.191.144:8020 successful
The arguments to the -failover command are the namenode that should be standby followed by the namenode that should become active.
0
0
Wrote my CCAH CCA-500 exam last weekend and passed with 93%! (The passing score now is 70%). Total 60 questions, most of them were about Hadoop Cluster Installation and Administration, HDFS, YARN and MapReduce version 2 (MRv2) and Hadoop Cluster Planning(about 75% of all questions were on those 4 points), also, some questions (25% more or less) on Resource Management and Monitoring and Logging. I used premium CCA-500 dumps (pdf and vce dumps here: https://tr.im/3CEJa) for preparing for the exam, all questions were available in that premium dumps, 100% valid now.
0
0
Good Promotion for Passleaders
0
0
C is correct….ref link:http://www.cloudera.com/documentation/enterprise/5-3-x/topics/cdh_hag_hdfs_ha_admin.html
0
0
C is write answer – With -failover 1st goes standby while 2nd become active
0
0
should be B。
from the definitive guide。
The transition from the active namenode to the standby is managed by a new entity in the system called the failover controller. There are various failover controllers, but the default implementation uses ZooKeeper to ensure that only one namenode is active. Each namenode runs a lightweight failover controller process whose job it is to monitor its namenode for failures (using a simple heartbeating mechanism) and trigger a failover should a namenode fail.
Failover may also be initiated manually by an administrator, for example, in the case of routine maintenance. This is known as a graceful failover, since the failover controller arranges an orderly transition for both namenodes to switch roles.
In the case of an ungraceful failover, however, it is impossible to be sure that the failed namenode has stopped running. For example, a slow network or a network partition can trigger a failover transition, even though the previously active namenode is still running and thinks it is still the active namenode. The HA implementation goes to great lengths to ensure that the previously active namenode is prevented from doing any damage and causing corruption — a method known as fencing.
0
0
b and c is correct but this phenomena is know as fenceing so should go or b only
0
0
http://www.cloudera.com/documentation/enterprise/5-6-x/topics/cdh_hag_hdfs_ha_admin.html
Manually Failing Over to the Standby NameNode Using the Command Line
To initiate a failover between two NameNodes, run the command hdfs haadmin -failover.
This command causes a failover from the first provided NameNode to the second. If the first NameNode is in the Standby state, this command simply transitions the second to the Active state without error. If the first NameNode is in the Active state, an attempt will be made to gracefully transition it to the Standby state. If this fails, the fencing methods (as configured by dfs.ha.fencing.methods) will be attempted in order until one of the methods succeeds.
0
0
The correct is C.
——–
hdfs haadmin -failover
——–
Example: In the following snapshot, by issuing the command in the shell. Namenode “nn1”, which was in active state switched to standby
0
0
This subcommand causes a failover from the first provided NameNode to the second. If the first NameNode is in the Standby state, this command simply transitions the second to the Active state without error. If the first NameNode is in the Active state, an attempt will be made to gracefully transition it to the Standby state. If this fails, the fencing methods (as configured by dfs.ha.fencing.methods) will be attempted in order until one succeeds. Only after this process will the second NameNode be transitioned to the Active state. If no fencing method succeeds, the second NameNode will not be transitioned to the Active state, and an error will be returned.
0
0
OPtion C is correct .
nn01 will not be fenced , no suchthing .
This command causes a failover from the first provided NameNode to the second. If the first NameNode is in the Standby state, this command simply transitions the second to the Active state without error. If the first NameNode is in the Active state, an attempt will be made to gracefully transition it to the Standby state. If this fails, the fencing methods (as configured by dfs.ha.fencing.methods) will be attempted in order until one of the methods succeeds. Only after this process will the second NameNode be transitioned to the Active state. If no fencing method succeeds, the second NameNode will not be transitioned to the Active state, and an error will be returned.
0
0
I have the same idea. B
0
0
The Correct answer is B.
0
0