Hi all,
I'm Alberto Chiusole, an Italian computer science student and
open-source fan.
I'm currently performing a small research to expose to my fellow
students the Hadoop project, and this is my first post in this ML.
I think I spotted I small mistake in the HDFS documentation regarding
achieving HA with the Quorum Journal Manager [1], section "Hardware
resources", paragraph "JournalNode machines": it's stated:
"""
The JournalNode daemon is relatively lightweight, so these daemons may
reasonably be collocated on machines with other Hadoop daemons, for
example NameNodes, the JobTracker, (...)
"""
Is "NameNodes" a typo and you meant "DataNode" instead? Aren't the
JournalNodes meant to survive in case of a failure of the NameNodes? Why
should I place a JournalNode on the same machine that contains the log I
need to synchronize?
Moreover I have a quick question on the same topic: why do you suggest
to place an odd numbers of machines as JournalNodes in order to increase
the Fault Tolerance?
Regards,
Alberto Chiusole
[1]:
https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HDFSHighAvailabilityWithQJM.html#Hardware_resources
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