Here are some lines I copied from “OCFS2 Support Guide – On-Disk Format”
Truncate logs help to improve the delete performance. This system file allows the fs to collect freed bits and flush it to the global bitmap in chunks. What that also means is that space could be temporarily “lost” from the fs. As in, the space freed by deleting a large file may not show up immediately. One can view the orphan_dirs and the truncate_logs to account for such “lost” space.
To view a truncate log, do:
The truncate_log keeps records of start cluster# and number of clusters. The max number of such records “Total Records” depend on the block size. The above is for a 4K block size.