This must be novice topic for the list, please excuse the ignorance. When it comes to log write scheme in XFS, I wonder if I can draw parallel with any journaling mode of Ext4 (ordered or writeback)? I checked xlog_sync() code, and found that each log IO is marked with PREFLUSH and FUA (for internal log case). This perhaps makes it similar to "ordered" journal mode of Ext4. But I am not sure about exact intent of choosing PREFLUSH for log write i.e.whether it is for all previous non-log IO (meta and data) or only for meta-IO. Nor I am sure whether xfs makes a conscious choice to issue data writes before meta or journal I/Os. Thanks, -- Joshi
