16 December 2008
During my daily browsing of the web, I read about a concept that I have never considered before: atomicity. This concept usually refers to database transactions and means that the transaction will either completely succeed or completely fail. Journaled filesystems make use of this system in the event of a crash. Before your computer commits data to the disc, it logs what it will do to a file, called a journal, before actually committing the change, called a transaction. If the computer crashes before it finishes writing the data to the disk then the log will be incomplete. When the computer restarts, the filesystem’s journal will be replayed; incomplete entries are ignored and reverted to the most recent complete entry. Thus, if the data was not written correctly and completely, it will not be written at all.
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