4 ms·

Hmm, I've seen old HDDs fail to spin up or otherwise have catastrophic malfunction, but never heard of them having real bit rot. I recently booted up some port

Hmm, I've seen old HDDs fail to spin up or otherwise have catastrophic malfunction, but never heard of them having real bit rot. I recently booted up some portable PCs from around 1990 to review their HDD content and scrub the disk state before handing them over as e-waste. Easily 25 years on the shelf. I would think you'd have to do something very wrong like storing the HDD near a degausser to lose the magnetic recording. I do think that SSDs and particularly cheap flash "thumb drives" are capable of having bit rot when left on the shelf for many years.

vel0city 3y ago
Did you actually validate every bit was exactly right on the drive? Did you even have the information to validate that data? Not just that they booted up without a noticeable error, but that every bit was exactly as written 25 years ago? How many drives did you test, how many manufacturers? Most of the bits will probably be fine. Some of them probably won't be. The rate depends on a myriad of factors. Even within a brand different models will be better or worse, and it's not exactly a metric you'll find listed. And then yes the way they're stored is also a factor and even the environment when the data was written. I've had drives from the 80s still work and still pretty much have all the data. I've had files get corrupted on modern drives with no other explanation than bitrot. Even just cosmic rays can eventually flip some bits.
- saltcured 3y ago
  Fair enough, I did not have checksums to compare. And I only randomly sampled the contents, not every single file. But yes, it booted and every program I tried executed normally and every data file I inspected seemed valid. I do have some familiarity with how such old systems would misbehave with corrupt data, such as from bad data cables. I didn't see any of those kinds of symptoms and so do not think there was any significant storage decay from being on the shelf at least 5x longer than the 5 year interval mentioned up thread. I tend to think that such a failing drive must have had some other kind of damage and not just some kind of spontaneous demagnetization
  - vel0city 3y ago
    Another thing to remember is some of the really older disks will have larger magnetic areas as platter density wasn't nearly as much. As densities increased the amount of total charge per bit decreased as there's just less magnetic material available. Just one of the many factors of how likely you are to experience any issues. Refreshing every five years for magnetic storage is probably overly cautious to me from my own personal experiences. But FWIW if it's data I really care about it doesn't spend years sitting around on just magnetic media. For my own personal risk tolerance putting important data on say an external hard drive and sticking it on a shelf isn't a great way to archive data. I might do it with data I'm OK with eventually maybe losing, but if it's something I know I'll want in 20+ years it gets a few copies with one being on some highly reliable optical media like M-DISC. Your hard drive might go a long, long time without losing a bit. And maybe if you do lose some data, it's a couple of typos in some help file. Maybe it's some rare code path in an executable that almost never gets called. Maybe it's some b-frame in a video that you'd never even notice. Maybe it's some important bits of the last photo you had of a loved one. Maybe it's some important field a database. Maybe it was empty space. Who knows.

vel0city 3y ago

Did you actually validate every bit was exactly right on the drive? Did you even have the information to validate that data? Not just that they booted up without a noticeable error, but that every bit was exactly as written 25 years ago? How many drives did you test, how many manufacturers? Most of the bits will probably be fine. Some of them probably won't be. The rate depends on a myriad of factors. Even within a brand different models will be better or worse, and it's not exactly a metric you'll find listed. And then yes the way they're stored is also a factor and even the environment when the data was written. I've had drives from the 80s still work and still pretty much have all the data. I've had files get corrupted on modern drives with no other explanation than bitrot. Even just cosmic rays can eventually flip some bits.

saltcured 3y ago
Fair enough, I did not have checksums to compare. And I only randomly sampled the contents, not every single file. But yes, it booted and every program I tried executed normally and every data file I inspected seemed valid. I do have some familiarity with how such old systems would misbehave with corrupt data, such as from bad data cables. I didn't see any of those kinds of symptoms and so do not think there was any significant storage decay from being on the shelf at least 5x longer than the 5 year interval mentioned up thread. I tend to think that such a failing drive must have had some other kind of damage and not just some kind of spontaneous demagnetization
- vel0city 3y ago
  Another thing to remember is some of the really older disks will have larger magnetic areas as platter density wasn't nearly as much. As densities increased the amount of total charge per bit decreased as there's just less magnetic material available. Just one of the many factors of how likely you are to experience any issues. Refreshing every five years for magnetic storage is probably overly cautious to me from my own personal experiences. But FWIW if it's data I really care about it doesn't spend years sitting around on just magnetic media. For my own personal risk tolerance putting important data on say an external hard drive and sticking it on a shelf isn't a great way to archive data. I might do it with data I'm OK with eventually maybe losing, but if it's something I know I'll want in 20+ years it gets a few copies with one being on some highly reliable optical media like M-DISC. Your hard drive might go a long, long time without losing a bit. And maybe if you do lose some data, it's a couple of typos in some help file. Maybe it's some rare code path in an executable that almost never gets called. Maybe it's some b-frame in a video that you'd never even notice. Maybe it's some important bits of the last photo you had of a loved one. Maybe it's some important field a database. Maybe it was empty space. Who knows.