Neil Brown <neilb@xxxxxxxxxxxxxxx> wrote: > On Tuesday January 4, ptb@xxxxxxxxxxxxxx wrote: > > Bits flip on our client disks all the time :(. > > You seem to be alone in reporting this. I certainly have never > experienced anything quite like what you seem to be reporting. I don't feel the need to prove it to you via actual evidence. You already know of mechanisms which produce such an effect: > Certainly there are reports of flipped bits in memory. .. and that is all the same to your code when it comes to resyncing. You don't care whether the change is real or produced in the cpu, on the bus, or wherever. It still is what you will observe and copy. > If you have > non-ecc memory, then this is a real risk and when it happens you > replace the memory. Sure. > Usually it happens with a sufficiently high > frequency that the computer is effectively unusable. Well, there are many computers that remain usable. When I see bit flips the first thing I request the techs to do is check the memory and keep on checking it until they find a fault. I also ask them to check the fans, clean out dust and so on. In a relatively small percentage of cases, it turns out that the changes are real, on the disk, and persist from reboot to reboot, and move with the disk when one moves it from place to place. I don't know where these come from - perhaps from the drive electronics, perhaps from the disk. > But bits being flipped on disk, without the drive reporting an error, > and without the filesystem very quickly becoming unusable, is (except > for your report) unheard of. As far as I recall it is usually a bit flipped througout a range of consecutive addresses on disk, when it happens. I haven't been monitoring this daily check for about a year now, however, so I don't have any data to show you. > md/raid would definitely not help that sort of situation at all. Nor is there any reason to suggest it should - it just doesn't check. It could. Peter - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
