This is an updated implementation of journal guided resync, intended to be suitable for production systems. This feature addresses the problem with RAID arrays that take too long to resync - similar to the existing MD write-intent bitmap feature, we resync only the stripes that were undergoing writes at the time of the crash. Unlike write-intent bitmaps, our testing shows very little performance degredation as a result of the feature - around 3-5% vs around 30% for bitmaps. This feature is based on work described in this paper: http://www.usenix.org/events/fast05/tech/denehy.html As a summary, we introduce a new data write mode known as declared mode. This is based on ordered mode except that a list of blocks to be written during the current transaction is added to the journal before the blocks themselves are written to the disk. Then, if the system crashes, we can resync only those blocks during journal replay and skip the rest of the resync of the RAID array. The changes consist of patches to ext3, jbd, MD, and the raid456 personality. These patches are currently against the RHEL 5 kernel 2.6.18-128.1.6. Porting to ext4/jbd2 and a more modern kernel is a TODO item. Cheers, Jody -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
