#Extfs list orphaned inodes free#
#Extfs list orphaned inodes windows#

Changes to the journal may themselves be journaled for additional redundancy, or the journal may be distributed across multiple physical volumes to protect against device failure. Some file systems may also allow external journals on a separate device, such as a solid-state drive or battery-backed non-volatile RAM. Some file systems allow the journal to grow, shrink and be re-allocated just as a regular file, while others put the journal in a contiguous area or a hidden file that is guaranteed not to move or change size while the file system is mounted. The changes are thus said to be atomic (not divisible) in that they either succeed (succeeded originally or are replayed completely during recovery), or are not replayed at all (are skipped because they had not yet been completely written to the journal before the crash occurred). After a crash, recovery simply involves reading the journal from the file system and replaying changes from this journal until the file system is consistent again. To prevent this, a journaled file system allocates a special area-the journal-in which it records the changes it will make ahead of time.

If the file system is large and if there is relatively little I/O bandwidth, this can take a long time and result in longer downtimes if it blocks the rest of the system from coming back online. This must typically be done before the file system is next mounted for read-write access. On the other hand, if step 2 preceded step 1, a crash between them would cause the file to be inaccessible, despite appearing to exist.ĭetecting and recovering from such inconsistencies normally requires a complete walk of its data structures, for example by a tool such as fsck (the file system checker). If step 3 preceded step 1, a crash between them could allow the file's blocks to be reused for a new file, meaning the partially deleted file would contain part of the contents of another file, and modifications to either file would show up in both. Re-arranging the steps does not help, either.

If a crash occurs after step 1 and before step 2, there will be an orphaned inode and hence a storage leak if a crash occurs between steps 2 and 3, then the blocks previously used by the file cannot be used for new files, effectively decreasing the storage capacity of the file system.

#Extfs list orphaned inodes free#

Returning all disk blocks to the pool of free disk blocks.Releasing the inode to the pool of free inodes.įor example, deleting a file on a Unix file system involves three steps: This makes it possible for an interruption (like a power failure or system crash) between writes to leave data structures in an invalid intermediate state. Updating file systems to reflect changes to files and directories usually requires many separate write operations.

#Extfs list orphaned inodes windows#

This was subsequently implemented in Microsoft's Windows NT's NTFS filesystem in 1993 and in Linux's ext3 filesystem in 2001. The next year the idea was popularized in a widely cited paper on log-structured file systems. In 1990 IBM introduced JFS in AIX 3.1 as one of the first UNIX commercial filesystems that implemented journaling.