Data stored on disk.

Hummingbird's disk storage is segmented into four regions:

• clusters, which store the file data and meta-data,
• mappings of files to clusters, which allow a file to be quickly located on disk by identifying which clusters the file is in,
• the hot cluster log, which caches frequently used clusters, and
• the delete log, which stores small records describing intentional deletes.

The mappings of files to clusters is part of the file meta-data described in Section 3.2.