On Tue, 1 Jul 2014 14:30:07 Rohan McLeod wrote: > >> Presumably as a probabilistic phenomenon; bitrot might be defined in > >> terms of the half-life of the data ? > > > > http://research.cs.wisc.edu/adsl/Publications/corruption-fast08.html > > > > The above paper is the best reference I've seen. Half-life isn't a good > > measure as you can expect to lose ~50 sectors at a time on a TB+ disk. > > Thanks for responding Russell > This paper doesn't seem to distinguish between corruption attributable > to drive 'malfunction' and > corruption which would have happened anyway ? eg while the drive was > switched off
Their business is in running drives 24*7, as is almost everyone who would have such statistics. Someone might do some research on drives maintaining data when turned off, but it seems unlikely that someone would have good access to both types of data. Also they only care about data loss not why it happens. Maybe someone at archive.org could do something in that area. > But I notice : > "/(ii) checksum mismatches within the same disk are not independent > events and > they show high spatial and temporal locality,"/ > Presumably bitrot due to temperature would not show " high spatial > locality " ? Silent bitrot doesn't tend to happen due to temperature, the Curie point would be well above the temperature for mechanical failure. In the disks that I've seen fail when overheated there has been obvious spatial locality, but I haven't seen a statistically significant sample. > https://en.wikipedia.org/wiki/Curie_temperature ; > so perhaps we can deduce cosmic rays a more likely cause, than > temperature ? Cosmic rays doesn't seem a likely cause. The steel case of a PC, the steel case of the hard drive, and whatever building you live in all cut down radiation. Something going wrong when data is written seems to be the most likely cause. Although it's worth noting that the ZFS "resilver" option must be there for a reason so I guess there's some data loss over time. But that might be due to writing adjacent tracks. -- My Main Blog http://etbe.coker.com.au/ My Documents Blog http://doc.coker.com.au/ _______________________________________________ luv-main mailing list [email protected] http://lists.luv.asn.au/listinfo/luv-main
