In this post, kyuusaku wrote:
17daysolderthannes wrote:
come again? are you saying magnetic media is GOOD for long term data archival? no...you can't possibly be saying that. Magnetic media is the sole reason we have the "backup copy" laws we do because magnetic media is prone to degradation over time no matter how you store it (spare maybe some über ridiculous vacuum chamber of magic or something). As far as I know, flash storage is the only permanent storage method without degradation, but there could be others I'm just not thinking of at the moment.
Yes, I mean what I said. Flash is not a perfect storage medium, not even close. Flash is easily one of the worst storage mediums since it's prone to electrical damage, overwriting, block erasal, and most importantly: it attempts to retain a charge indefinitely to determine a bit state.
Flash memory isn't THAT bad. Most microcontrollers these days (all?) that don't use mask ROMs use flash. We use flash on our controls at work that run 24/7 365 days a year. Never seen one lose their mind yet. There's several thousand of them running all day every day.
Newer aircraft "black boxes" are using flash these days instead of the magnetic wire 'cause it is more reliable, easy to test, and survives the crash better apparently.
Flash uses tunneling to inject charges into a floating gate oxide. Retention is spec'd at 40-100 years in the datasheet (depending on device). Those electrons, once trapped, REALLY don't want to go anywhere
As for "block erasal", flash IS rewritable, so of course there are methods to erase it. This is no different from a floppy where there's an erase/write head. Unless the chip has a design flaw, the charge pump doesn't even come on unless an erase is initiated. Without this charge pump, you cannot erase the flash no way no how. You need a potential of around 12V for tunneling to take place.
Electrical damage isn't much of an issue either; the problems are easily managed (overvoltage protection devices), ESD protection (integral to the chip, and you can provide your own external stuff too).
I personally cannot wait until we have some flash based HD replacements. With proper wear-levelling techniques, they will outlast just about any machine they are placed in. Even a 20-40 gig flash drive would be incredibly useful since you can put your OS and swap on there and get kickass access times.