1 Answers

What is the maximum number of NameNodes daemon you should run on you cluster in order to avoid a “split-brain” scenario with your NameNodes?

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CCA-410

You configure you cluster with HDFS High Availability (HA) using Quorum-Based storage. You do
not implement HDFS Federation.
What is the maximum number of NameNodes daemon you should run on you cluster in order to
avoid a “split-brain” scenario with your NameNodes?

A.
Unlimited. HDFS High Availability (HA) is designed to overcome limitations on the number of
NameNodes you can deploy.

B.
Two active NameNodes and one Standby NameNode

C.
One active NameNode and one Standby NameNode

D.
Two active NameNodes and two Standby NameNodes

1 Answers



  1. intmin on Jul 24, 2013 Reply

    Answers: C
    One active NameNode and one Standby NameNode

    Explanation:
    In a typical HA cluster, two separate machines are configured as NameNodes. At
    any point in time, one of the NameNodes is in an Active state, and the other is in a Standby state.
    The Active NameNode is responsible for all client operations in the cluster, while the Standby is
    simply acting as a slave, maintaining enough state to provide a fast failover if necessary.
    Note: It is vital for the correct operation of an HA cluster that only one of the NameNodes be active
    at a time. Otherwise, the namespace state would quickly diverge between the two, risking data
    loss or other incorrect results. In order to ensure this property and prevent the so-called “split-brain
    scenario,” the JournalNodes will only ever allow a single NameNode to be a writer at a time.
    During a failover, the NameNode which is to become active will simply take over the role of writing
    to the JournalNodes, which will effectively prevent the other NameNode from continuing in the
    Active state, allowing the new Active NameNode to safely proceed with failover.
    Cloudera CDH4 High Availability Guide, Quorum-based Storage

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