This is all well and good but it would be I think most effective if drives had their own battery backed write-back cache which can be pinned by the OS to the journal. If the feature can be made persistent, by committing the data to flash or something on drive shutdown, then the data doesn't even need to be committed to the disk. It seems to me that this kind of design could remove inherent penalties associated with journaling using proper write barriers. This kind of technology could use used for transactional databases as well by making the transaction record work at memory and interface speed rather than be limited by the rotational speed of the drives. This should reduce contention on the platters by removing one of the more constant sources of activity.
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