3 ms·

Multiple-bits-per-cell is astonishingly involved; with three bits the electronics has to distinguish between eight voltage levels in the face of process variati

by kabdib 10y ago

Multiple-bits-per-cell is astonishingly involved; with three bits the electronics has to distinguish between eight voltage levels in the face of process variations and environmental conditions that vary widly. There aren't that many electrons in these cells to begin with, and the charges leak over time. I think of the engineering that goes into this stuff as "heroic." 4 bits per cell and you're talking full bull-goose crazy. My hat's off to ya (no, I'm not going to buy any of that). So you ECC the shit out of things and hope. Or you use less ECC, get more "checkbox capacity" on the box the consumer sees, and most people won't experience failure until they throw the device away. It's all about margins. SSDs, even the expensive ones you buy, don't have a super long shelf life and are not what you want to use for backup media.

FullyFunctional 10y ago
This, a million times, this. It's a stunning paradox that densities and adoption is growing dramatically all the while raw retention gets worse with every generation (an astonishing amount of smarts goes into mitigating media deficiencies). I'm not too concerned (assuming the standard backups) about devices in continuous and powered-on use, but for data at rest, powered off, this is very scary.
- kabdib 10y ago
  It gets even more scary: So you back up all your data to disks? Sure, they're pretty cheap and you can buy a terabyte for fifty bucks, but guess what the firmware for those drives is stored on. Hope the flash they used wasn't cheap (but if it's a consumer drive and it cost you fifty bucks, it probably was). For long life I'm betting on DVDs (refreshed every few years). Easily half of the 15 year old drives I've been keeping are now bad; copying them forward every few years is a good idea. It might be time to go back to tape, but it's expensive. Pretty much everything sucks at retention.
  - pathikrit 10y ago
    Or just pay $100/yr to back it up to Dropbox (or even cheaper AWS Glacier)?

by kabdib 10y ago

FullyFunctional 10y ago

This, a million times, this. It's a stunning paradox that densities and adoption is growing dramatically all the while raw retention gets worse with every generation (an astonishing amount of smarts goes into mitigating media deficiencies). I'm not too concerned (assuming the standard backups) about devices in continuous and powered-on use, but for data at rest, powered off, this is very scary.

kabdib 10y ago
It gets even more scary: So you back up all your data to disks? Sure, they're pretty cheap and you can buy a terabyte for fifty bucks, but guess what the firmware for those drives is stored on. Hope the flash they used wasn't cheap (but if it's a consumer drive and it cost you fifty bucks, it probably was). For long life I'm betting on DVDs (refreshed every few years). Easily half of the 15 year old drives I've been keeping are now bad; copying them forward every few years is a good idea. It might be time to go back to tape, but it's expensive. Pretty much everything sucks at retention.
- pathikrit 10y ago
  Or just pay $100/yr to back it up to Dropbox (or even cheaper AWS Glacier)?