>>>> --- >>>> There are storage devices that high highly undesirable properties >>>> when they are disconnected or suffer power failures while writes are >>>> in progress; such devices include flash devices and MD RAID 4/5/6 >>>> arrays. These devices have the property of potentially >>>> corrupting blocks being written at the time of the power failure, and >>>> worse yet, amplifying the region where blocks are corrupted such that >>>> additional sectors are also damaged during the power failure. >>> >>> I would strike the entire mention of MD devices since it is your >>> assertion, not a proven fact. You will cause more data loss from common >> >> That actually is a fact. That's how MD RAID 5 is designed. And btw >> those are originaly Ted's words. > > Ted did not design MD RAID5. So what? He clearly knows how it works. Instead of arguing he's wrong, will you simply label everything as unproven? >>> events (single sector errors, complete drive failure) by steering people >>> away from more reliable storage configurations because of a really rare >>> edge case (power failure during split write to two raid members while >>> doing a RAID rebuild). >> >> I'm not sure what's rare about power failures. Unlike single sector >> errors, my machine actually has a button that produces exactly that >> event. Running degraded raid5 arrays for extended periods may be >> slightly unusual configuration, but I suspect people should just do >> that for testing. (And from the discussion, people seem to think that >> degraded raid5 is equivalent to raid0). > > Power failures after a full drive failure with a split write during a rebuild? Look, I don't need full drive failure for this to happen. I can just remove one disk from array. I don't need power failure, I can just press the power button. I don't even need to rebuild anything, I can just write to degraded array. Given that all events are under my control, statistics make little sense here. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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
