Journaling is a widely used technique to increase file system robustness against metadata and/or data corruptions. While the overhead of journaling can be masked by the page cache for small-scale, local file systems, the authors found that Lustre’s use of journaling for the object store significantly impacted the overall performance of their large-scale centerwide parallel file system. By requiring that each write request wait for a journal transaction to commit, Lustre introduced serialization to the client request stream and imposed additional latency due to disk head movement (seeks) for each request.
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