Austin S. Hemmelgarn posted on Tue, 15 Dec 2015 11:00:40 -0500 as excerpted:
> And in particular, the only > journaling filesystem that I know of that even allows the option of > journaling the file contents instead of just metadata is ext4. IIRC, ext3 was the first to have it in Linux mainline, with data=writeback for the speed freaks that don't care about data loss, data=ordered as the default normal option (except for that infamous period when Linus lost his head and let people talk him into switching to data=writeback, despite the risks... he later came back to his senses and reverted that), and data=journal for the folks that were willing to pay trade a bit of speed for better data protection (tho it was famous for surprising everybody, in that in certain use-cases it was extremely fast, faster than data=writeback, something I don't think was ever fully explained). To my knowledge ext3 still has that, tho I haven't used it probably a decade. Reiserfs has all three data= options as well, with data=ordered the default, tho it only had data=writeback initially. While I've used reiserfs for years, it has always been with the default data=ordered since that was introduced, and I'd be surprised if data=journal had the same use-case speed advantage that it did on ext3, as it's too different. Meanwhile, that early data=writeback default is where reiserfs got its ill repute for data loss, but it had long switched to data=ordered by default by the time Linus lost his senses and tried data=writeback by default on ext3. Because I was on reiserfs from data=writeback era, I was rather glad most kernel hackers didn't want to touch it by the time Linus let them talk him into data=writeback on ext3, and thus left reiserfs (which again had long been data=ordered by default by then) well enough alone. But I did help a few people running ext3 trace down their new ext3 stability issues to that bad data=writeback experiment, and persuaded them to specify data=ordered, which solved their problems, so indeed they /were/ data=writeback related. And happily, Linus did eventually regain his senses and return ext3 to data=ordered by default once again. And based on what you said, ext4 still has all three data= options, including data=journal. But I wasn't sure on that myself (tho I would have assumed it inherited it from ext3) and thus am /definitely/ not sure whether it inherits ext3's data=journal speed advantages in certain corner-cases. I have no idea whether other journaled filesystems allow choosing the journal level or not, tho. I only know of those three. -- Duncan - List replies preferred. No HTML msgs. "Every nonfree program has a lord, a master -- and if you use the program, he is your master." Richard Stallman -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
