During Node Migration MISSING/CORRUPT Blocks Cause StartHadoopServices Failure As NameNodes Go Into SafeMode (Doc ID 2191478.1)

Last updated on OCTOBER 13, 2016

Applies to:

Big Data Appliance Integrated Software - Version 4.3.0 and later
Linux x86-64

Symptoms

When performing node migration, there are a set of mandatory prerequisites to follow. These are listed in the "Mandatory Prerequisites" section of the document: Node Migration on Oracle Big Data Appliance V4.0 OL6 Hadoop Cluster to Manage a Hardware Failure (Doc ID 1946210.1).

One of the prerequisites is to cleanup any missing/corrupt blocks to prevent the Active/Standby NameNodes  from going into safemode when services are restarted. The hdfs filesystem should be in "good" health when performing the migration (except for the failed node).

It may not be possible to clean up missing/corrupt blocks and restore the hdfs file system into "good" health when node migration needs to be performed.  In this case, the node migration step to start Hadoop services,"StartHadoopServices", will fail because this condition causes NameNodes to go into safemode and remain in that state.

Cause

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