> > +Either whole sector is correctly written or nothing is written during > > +powerfail. > > + > > + Because RAM tends to fail faster than rest of system during > > + powerfail, special hw killing DMA transfers may be necessary; > > + otherwise, disks may write garbage during powerfail. > > + This may be quite common on generic PC machines. > > + > > + Note that atomic write is very hard to guarantee for RAID-4/5/6, > > + because it needs to write both changed data, and parity, to > > + different disks. (But it will only really show up in degraded mode). > > + UPS for RAID array should help. > > Can someone clarify if this is true in raid-6 with just a single disk > failure? I don't see why it would be. > > And if not can the above text be changed to reflect raid 4/5 with a > single disk failure and raid 6 with a double disk failure are the > modes that have atomicity problems. I don't know enough about raid-6, but... I said "degraded mode" above, and you can read it as double failure in raid-6 case ;-). I'll prefer to avoid too many details here. -- (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
