I have worked through my listening to the Security Now! podcasts up to middle October now (more specifically up to here) and one remark from Steve Gibson forced me to think very hard: how today's hard drives encounter hundreds of read errors a day (actually Leo said "hundreds a minute"), but thanks to ECC process and dynamic reallocation of sectors, this is invisible to the user, because:
" .... if a file is damaged because of a bad sector, it can recover that data by recovering the data, either moving it or kind of reformatting the sector underneath it to make it readable again ... "
as well as
" Drives have gotten so dense that drives are now depending upon the error correction code, ECC, just to read good sectors, not even bad sectors...."
This made me really worried. I was deciding right now to buy the RAID-5 NAS storage (1 TB or 2 TB), because I always considered hard drive the most reliable storage medium: better than DVD and much better than very unreliable CDR (which are unreasonably small anyway). My line of thinking was: I want to get as large disks as I can within the budget.
The trend of increasing densities and decreasing the price of hard disks leads us "probabilistic" information storage. Imagining how my hard disks keep reallocating sectors and that the deliver data only because some correction codes works on fixing errors that occur every minute ... ouch. Despite of that, the hard drive manufactures keep offering 3 to 5 years warranties on most drives. This may look good in theory, but I do not really care that I will get back my $96 for the failed 250 GB hard disk. Loosing 250 GB of images and videos is a big deal. And the only way how to back up such amount of data in home environment - is to use another harddrive, unfortunately.
Maybe trying to get as big hard disk as possible is not the smartest approach. The smallest hard disk one can buy these days is about 80 GB (~ $50) with the largest in range of 400-500 GB. What is the ideal ballance between size, price and reliability ? That's a very good question.