4 ms·

If persistent Flash memory has RAM-like characteristics, why are we still treating it like it's a spinning disk? I'm not sure we are (other than low-level deta

by neilc 16y ago

If persistent Flash memory has RAM-like characteristics, why are we still treating it like it's a spinning disk? I'm not sure we are (other than low-level details like how the kernel does I/O scheduling and filesystem implementation details). RAM is transient; SSDs and magnetic disk are both persistent. Hence, both SSDs and magnetic disk can serve as stable storage. SSDs and HDs have different performance characteristics, but I'm not so sure that a radical rethinking of the storage hierarchy is actually called for. a big reason our lengthy boot-up procedure even exists is because we had to have a spinning disk Offhand, I would guess that a big reason for lengthy bootups is the time required to probe, detect and configure hardware (plus latency stuff like BIOS init). An intelligent OS will be able to arrange the disk I/O that needs to be done on startup so it is mostly sequential; SSDs and HDs are not significantly different with respect to sequential read performance.

stcredzero 16y ago
RAM is transient; SSDs and magnetic disk are both persistent. Wow, somehow I missed this fact after 30 years of programming! both SSDs and magnetic disk can serve as stable storage Yes, but sometimes a quantitative difference can result in a qualitative one. (Like branching and merging and using historical information in Git. The fact that you can do this so quickly from the local Git repository means you can use it in ways that wouldn't be practical in something like Subversion.) Offhand, I would guess that a big reason for lengthy bootups is the time required to probe, detect and configure hardware Why doesn't this apply to hibernating laptops? (Or for that matter, the iPad?) In this day and age, to we always have to turn the power 100% off on a regular basis? Also, there are experimental OS like EROS, where there is no boot-up, only a reactivation of certain facilities like network cards. The lengthy boot-up process is now living on a set of cultural expectations. There is no longer a technical reason for its existing.
- neilc 16y ago
  Wow, somehow I missed this fact after 30 years of programming! Yay for sarcasm. My point is that changing the performance characteristics of the lower levels of the storage hierarchy does not necessarily mean we need to make radical changes. The lengthy boot-up process is now living on a set of cultural expectations. There is no longer a technical reason for its existing. Maybe so; my point was just that I don't see how SSDs vs. magnetic disk fundamentally effect the boot-up process. Hibernation vs. power-off is orthogonal to the type of storage used.
  - stcredzero 16y ago
    SSD can also have lower power requirements. Combine SSD with the cloud, and you can have something which can respond faster to the typical user while eliminating any thoughts about storage size and backups. If you just treat the Flash as RAM, with volatile RAM as a very large L3 cache, the notion of hard drive can just disappear. Everything just becomes orthogonally persistent. I'm guessing this is a troll. Most programmers I talk to in person just get this without so much exposition.

by neilc 16y ago

stcredzero 16y ago

RAM is transient; SSDs and magnetic disk are both persistent. Wow, somehow I missed this fact after 30 years of programming! both SSDs and magnetic disk can serve as stable storage Yes, but sometimes a quantitative difference can result in a qualitative one. (Like branching and merging and using historical information in Git. The fact that you can do this so quickly from the local Git repository means you can use it in ways that wouldn't be practical in something like Subversion.) Offhand, I would guess that a big reason for lengthy bootups is the time required to probe, detect and configure hardware Why doesn't this apply to hibernating laptops? (Or for that matter, the iPad?) In this day and age, to we always have to turn the power 100% off on a regular basis? Also, there are experimental OS like EROS, where there is no boot-up, only a reactivation of certain facilities like network cards. The lengthy boot-up process is now living on a set of cultural expectations. There is no longer a technical reason for its existing.

neilc 16y ago
Wow, somehow I missed this fact after 30 years of programming! Yay for sarcasm. My point is that changing the performance characteristics of the lower levels of the storage hierarchy does not necessarily mean we need to make radical changes. The lengthy boot-up process is now living on a set of cultural expectations. There is no longer a technical reason for its existing. Maybe so; my point was just that I don't see how SSDs vs. magnetic disk fundamentally effect the boot-up process. Hibernation vs. power-off is orthogonal to the type of storage used.
- stcredzero 16y ago
  SSD can also have lower power requirements. Combine SSD with the cloud, and you can have something which can respond faster to the typical user while eliminating any thoughts about storage size and backups. If you just treat the Flash as RAM, with volatile RAM as a very large L3 cache, the notion of hard drive can just disappear. Everything just becomes orthogonally persistent. I'm guessing this is a troll. Most programmers I talk to in person just get this without so much exposition.