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 Differences in df and du on Oracle Cluster File System (OCFS2) and Orphan Files — (18-August-2010)
Recently, it was noticed that the "df" and "du" commands were displaying different results from several nodes on two OCFS2 file systems. The cluster file systems were being used as shared storage for an Oracle RAC 10g configuration (Clusterware shared files and the Flash Recovery Area). Researching this problem yielded a bug with the OCFS2 kernel driver (1.4.2-1) that was apparently leaving deleted files in the orphan directory (the //orphan_dir name space in OCFS2) after being deleted from the disk. When an object (file and/or directory) is deleted from an OCFS2 cluster file system, the file system unlinks the object entry from the existing directory and links it as an entry against that cluster node's orphan directory (the //orphan_dir name space in OCFS2). When the object is eventually no longer used across the cluster, the file system frees it's inode including all disk space associated with it. It was determined that orphan files on the OCFS2 cluster file system were responsible for the significant difference between the df and du commands. OCFS2 was leaving some deleted files in the orphan directory (the //orphan_dir name space in OCFS2) after being deleted. The following article highlights the steps involved in troubleshooting disk space usage on an OCFS2 cluster file system and how to resolve the discrepancy between the df and du commands. Differences in df and du on Oracle Cluster File System (OCFS2) and Orphan Files ---------------------------- Jeffrey M. Hunter, OCP Sr. Database Administrator jhunter@idevelopment.info http://www.idevelopment.info ---------------------------- |