Below are three paragraphs from the RedHat White paper on ext3. The first paragraph says data=ordered is the default mode. The last paragraph says data=journal is the default mode. Which is correct? The second paragraph starting on the second line says that to journal metadata but not file data use data=ordered or data=writeback, This contradicts the first paragraph that says that data=ordered journals data. Which is correct? All this is very confusing, is it not? Any clarification would be appreciated. 1.The second mode, data=ordered (the default mode), guarantees that the data is consistent with the file system; recently-written files will never show up with garbage contents after a crash. 2. ext3 has multiple journaling modes. It can journal all file data and metadata (data=journal), or it can journal metadata but not file data (data=ordered or data=writeback). When not journaling file data, you can choose to write file system data before metadata (data=ordered; causes all metadata to point to valid data), or not to handle file data specially at all (data=writeback; file system will be consistent, but old data may appear in files after an unclean system shutdown). This gives the administrator the power to make the trade off between speed and file data consistency, and to tune speed for specialized usage patterns. 3. Red Hat is continuing to work on several performance enhancements to ext3, so you can expect several of these cases to improve in the future. This means that if you choose data=writeback now, you may want to retest the default data=journal with future releases to see what changes have been made relative to your workload. -- ------------------------------------------- Aaron Konstam Computer Science Trinity University 715 Stadium Dr. San Antonio, TX 78212-7200 telephone: (210)-999-7484 email:akonstam@trinity.edu -- Psyche-list mailing list Psyche-list@redhat.com https://listman.redhat.com/mailman/listinfo/psyche-list
