The Azure Blob Storage stores files in a flat key/value store without formal support for folders. The hadoop-azure file system layer simulates folders on top of Azure storage. By default, folder rename in the hadoop-azure file system layer is not atomic. This means that a failure during a folder rename could potentially leave some folders in the original directory and some in the new one.

Since HBase depends on atomic folder rename, a configuration setting called fs.azure.atomic.rename.dir can be set in core-site.xml to specify a comma-separated list of directories where folder rename is made atomic. If a folder rename fails, a redo will be applied to finish. A file <folderName>-renamePending.json may appear temporarily and is the record of the intention of the rename operation, to allow redo in event of a failure.

The default value of this setting is just /hbase. To list multiple directories, separate them with a comma. For example:

<property>
  <name>fs.azure.atomic.rename.dir</name>
  <value>/hbase,/data</value>
</property>