How freezing a hard drive is supposed to help? Does it make some bad blocks working again? Or does it make some bad blocks less bad, susceptible for retries? Or does it bring dead drives back to life like a magic?
Trying to understand and speculate on how freezing could help: - Cold air is denser than warm air and could lower the head flying height and thus make reading easier. Air density is 1.3943 at -20 C and 1.1455 at +35 C. Source: http://en.wikipedia.org/wiki/Density_of_air - If the drive uses thermal fly-height control, cold reduces the heater capability to bring the head closer the surface. If the cold exceeds the heating power, the head flies higher than was designed. http://www.hgst.com/tech/techlib.nsf/techdocs/98EE13311A54CAC886257171005E0F16/$file/TFC_whitepaper041807.pdf http://maeresearch.ucsd.edu/callafon/publications/2011/UweIEEETonM.pdf - Cold could make preamplifiers more sensitive by reducing noise. I wonder if -20C is cold enough to have effect on hard drive head preamplifiers? For example in some radio telescopes the preamplifier are cooled with liquid nitrogen. I speculate that some bad blocks are just too weak and noisy and require either more retries than drive can withstand or better signal to noise ratio ie. more correctly read bits. - Cold changes mechanics. Warped platters become less warped. Lubricants become stiffer. I have not yet tried freezing but probably will, once the drive I am currently trying to rescue reaches the point where I cannot fetch any more data at room temperature. After 2 weeks of running >99.9% is rescued and hoping to reach >99.99% before the freezing attempt. The splitting is over 100000 times slower than the initial reading of working areas. I am planning to use a plastic bag filled with silica gel grains and cold packs. The idea is to keep the drive cold as long as possible and at the same time as dry as possible. Cat litter is the cheapest source of silica gel and the idea came from this discussion at Slashdot: http://hardware.slashdot.org/story/08/05/12/2330200/a-walk-through-the-hard-drive-recovery-process Jarkko Lavinen _______________________________________________ Bug-ddrescue mailing list [email protected] https://lists.gnu.org/mailman/listinfo/bug-ddrescue
