Files still rotting in DFS of latest Hadoop
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Key: HADOOP-124
URL: http://issues.apache.org/jira/browse/HADOOP-124
Project: Hadoop
Type: Bug
Components: dfs
Environment: ~30 node cluster
Reporter: Bryan Pendleton
DFS files are still rotting.
I suspect that there's a problem with block accounting/detecting identical
hosts in the namenode. I have 30 physical nodes, with various numbers of local
disks, meaning that my current 'bin/hadoop dfs -report" shows 80 nodes after a
full restart. However, when I discovered the problem (which resulted in losing
about 500gb worth of temporary data because of missing blocks in some of the
larger chunks) -report showed 96 nodes. I suspect somehow there were extra
datanodes running against the same paths, and that the namenode was counting
those as replicated instances, which then showed up over-replicated, and one of
them was told to delete its local block, leading to the block actually getting
lost.
I will debug it more the next time the situation arises. This is at least the
5th time I've had a large amount of file data "rot" in DFS since January.
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