On Fri, 6 Nov 2015, Sami Tolvanen wrote: > On Fri, Nov 06, 2015 at 12:23:29PM -0500, Mikulas Patocka wrote: > > I'm also wondering what is this patch useful for. Disks and flash > > controllers have their own error detection and correction > > I think I addressed this earlier. Some storage devices are able to > correct bit flips, but don't have enough redundancy to correct larger > errors. Using this patch set we can correct N MiB of consecutive > corruption anywhere on the partition with the same amount of storage > overhead. So, why doesn't the patch correct I/O errors? It is more likely that the flash controller returns an I/O error than corrupted data. Why are you correcting corrupted data (that is unlikely) and not correcting I/O errors that are likely? > > Another point - if the read-only system partition is experiencing some > > errors, than the read-write partition will probably have errors too > > On mobile devices, errors in read-only partitions often lead to > bricked devices while errors in the read-write parts might only lead > to lost cat photos. There are situations where people would prefer to > have a working phone even if it fails to store some of their data. The read-write partition holds compiled applications and I doubt the smartphone would work if there were random bits flipped. > > Do you have some real case where such error corrections > > increase longevity of some device? > > Yes, there have been several cases where read-only partition errors > have rendered a device unusable. The sheer volume of mobile devices > means that even if a tiny fraction of them suffer from such a problem, > it's going to affect a large number of people. Why don't you reflash the device from bootloader? (by holding power and volume keys simultaneously on startup and using the fastboot utility) > > But you can take raid5 in read-only mode, put it on several partitions > > protected with dm-verity and you get decent error correction > > I agree. Unfortunately, we don't currently have the luxury of using > raid on mobile devices. Why not, it's just a simple kernel option. If raid5 already does data correction, there is no reason why to duplicate this work. > Sami Mikulas -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
