Tsz Wo (Nicholas), SZE created HDFS-5754:
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Summary: Split LayoutVerion into NamenodeLayoutVersion and
DatanodeLayoutVersion
Key: HDFS-5754
URL: https://issues.apache.org/jira/browse/HDFS-5754
Project: Hadoop HDFS
Issue Type: Sub-task
Components: datanode, namenode
Reporter: Tsz Wo (Nicholas), SZE
Currently, LayoutVersion defines the on-disk data format and supported features
of the entire cluster including NN and DNs. LayoutVersion is persisted in both
NN and DNs. When a NN/DN starts up, it checks its supported LayoutVersion
against the on-disk LayoutVersion. Also, a DN with a different LayoutVersion
than NN cannot register with the NN.
We propose to split LayoutVersion into two independent values that are local to
the nodes:
- NamenodeLayoutVersion - defines the on-disk data format in NN, including the
format of FSImage, editlog and the directory structure.
- DatanodeLayoutVersion - defines the on-disk data format in DN, including the
format of block data file, metadata file, block pool layout, and the directory
structure.
The LayoutVersion check will be removed in DN registration. If
NamenodeLayoutVersion or DatanodeLayoutVersion is changed in a rolling upgrade,
then only rollback is supported and downgrade is not.
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