5 ms·

Could easily reduce reliability.

Robotbeat 6y ago
It’s possible, just as increasing the density of NAND with 4 Levels per cell reduces write count. But can be countered by more careful engineering of the device.
- altcognito 6y ago
  NAND failures tend to be more localized though.
  - Robotbeat 6y ago
    This is probably not representative because it was using low grade USB flash devices from 10-15 years ago, but I think I’ve had more NAND flash failures than hard drive failures. I don’t think doubling the number of heads would make a huge difference as you wouldn’t be quite halving the reliability.
    - altcognito 6y ago
      Oh, I totally agree in that regard. Hard drive technology has been mature for a good number of decades, so a lot of the kinks have been worked out.
jacquesm 6y ago
No, it will reduce reliability. More parts = worse reliability.
- Robotbeat 6y ago
  Maybe? The issue is mechanical devices can be engineered until the reliability level needed is achieved. Sure, take the same device and double the numbers, you’ll have half the reliability, but you’ll also have more parts being made and more parts to amortize the reliability improvement engineering over (and more parts to get reliability statistics from... which also means you can test the rest of the hard drive faster, which can provide other reliability enhancements). NAND devices have similar constraints, actually, but they’re reaching more fundamental limits due to quantum effects and they’re generally addressed with software/firmware tricks like wear leveling.
  - jacquesm 6y ago
    > The issue is mechanical devices can be engineered until the reliability level needed is achieved. And if wishes were horses... No, you can not simply state some arbitrary level of reliability and design to that level. At any given level of reliability more parts = less reliability and more time or resources spent on design are not by going to remediate that unless you are willing to accept much higher costs. Engineering is a trade-off and physics determine the sweet spot for the balance of that trade off. Once that sweet spot has been determined all other things being equal more parts will cause your reliability to go down unless you will also accept that your costs will go up and/or other parameters will be affected in a negative way. Software people in general have a very hard time to understand this because to them 'parts' are free, but even in software, assuming zero costs for parts (adding a library, a function, a line of code) has an effect on reliability. That's why computers used to be much more reliable than they are today, and that's before we get into details such as cognitive load while trying to understand complex systems.

It’s possible, just as increasing the density of NAND with 4 Levels per cell reduces write count. But can be countered by more careful engineering of the device.

altcognito 6y ago
NAND failures tend to be more localized though.
- Robotbeat 6y ago
  This is probably not representative because it was using low grade USB flash devices from 10-15 years ago, but I think I’ve had more NAND flash failures than hard drive failures. I don’t think doubling the number of heads would make a huge difference as you wouldn’t be quite halving the reliability.
  - altcognito 6y ago
    Oh, I totally agree in that regard. Hard drive technology has been mature for a good number of decades, so a lot of the kinks have been worked out.

jacquesm 6y ago

No, it will reduce reliability. More parts = worse reliability.

Robotbeat 6y ago
Maybe? The issue is mechanical devices can be engineered until the reliability level needed is achieved. Sure, take the same device and double the numbers, you’ll have half the reliability, but you’ll also have more parts being made and more parts to amortize the reliability improvement engineering over (and more parts to get reliability statistics from... which also means you can test the rest of the hard drive faster, which can provide other reliability enhancements). NAND devices have similar constraints, actually, but they’re reaching more fundamental limits due to quantum effects and they’re generally addressed with software/firmware tricks like wear leveling.
- jacquesm 6y ago
  > The issue is mechanical devices can be engineered until the reliability level needed is achieved. And if wishes were horses... No, you can not simply state some arbitrary level of reliability and design to that level. At any given level of reliability more parts = less reliability and more time or resources spent on design are not by going to remediate that unless you are willing to accept much higher costs. Engineering is a trade-off and physics determine the sweet spot for the balance of that trade off. Once that sweet spot has been determined all other things being equal more parts will cause your reliability to go down unless you will also accept that your costs will go up and/or other parameters will be affected in a negative way. Software people in general have a very hard time to understand this because to them 'parts' are free, but even in software, assuming zero costs for parts (adding a library, a function, a line of code) has an effect on reliability. That's why computers used to be much more reliable than they are today, and that's before we get into details such as cognitive load while trying to understand complex systems.