A client application opens a file write stream on your cluster. Which two metadata changes occur during a file write?

Question

Options

• Athe namenode triggers a block report to update block locations in the edits file
• BThe change is written to the namenode disk
• CThe change is written to the edits file
• DThe metadata in a Ram on the name node is updated
• Ethe metadata in Ram on the namenode is flushed to disk
• Fthe change is written to the fsimage file
• Gthe change is written to the secondary namenode

• A
  2% (1)
• C
  78% (39)
• D
  2% (1)
• F
  6% (3)
• G
  12% (6)

Explanation

Note: Namenode stores modifications to the filesystem as a log appended to a native filesystem file (edits). When a Namenode starts up, it reads HDFS state from an image file (fsimage) and then applies edits from edits log file. It then writes new HDFS state to (fsimage) and starts normal operation with an empty edits file. Since namenode merges fsimage and edits files only during start up, edits file could get very large over time on a large cluster. Another side effect of larger edits file is that next restart of Namenade takes longer. The secondary namenode merges fsimage and edits log periodically and keeps edits log size with in a limit. It is usually run on a different machine than the primary Namenode since its memory requirements are on the same order as the primary namemode. The secondary namenode is started by bin/start-dfs.sh on the nodes specified in conf/masters file.

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