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You get some extra benefits too: You get rid of the split between memory and filesystem address space. In fact, you can kill off the traditional filesystem alto

You get some extra benefits too: You get rid of the split between memory and filesystem address space. In fact, you can kill off the traditional filesystem altogether. I'm excited by that, filesystems are a dirty kludge. But this would require completely changing how modern operating systems work. No doubt applications developers would love it though.

ithkuil 14y ago
do you mean filesystems as the hierarchical way to organize stuff or the filesystem implementation that ensures that data remains persisted also in the event of unflushed writes in case of crash/poweroff etc ?
- spitfire 14y ago
  Both, but much more the second. disks and filesystems as a weird, separate appendage hanging off the side of a computer are conceptually a weak idea. Once you've unified your address space - stable storage is in the same space as unstable storage, then your entire world changes. The trick then becomes, how do you represent objects (Hint: Others have already tread this ground, see AS/400).
  - ithkuil 14y ago
    Although many of the problems (i.e. seek time) of rotating disks are overcome by solid state persistent memory, you still need special datastructures to ensure that: a) data is buffered during write and that a power failure won't leave the storage in an inconsistent state b) blocks to be overwritten are reallocated and erased in background (you cannot simply overwrite a flash block before erasing it) c) the used datastructures (trees etc) are optimized for the size of the flash block d) gracefully handle block corruption Since it should be possible to remap blocks (either because of (b) or corruption (d)) it's common to have a logical block remapping layer somewhere in the (disk) controller. At this point classical filesystem algorithms and datastructure can easily solve the remaining problems (consistency with journaling and block optimized access like on rotating disks). Of course, there is another approach for solving (b): see http://en.wikipedia.org/wiki/Log-structured_file_system http://en.wikipedia.org/wiki/Log-structured_file_system (actually, log structured filesystem technique can be used to implement the block remapping within the ssd compatibility layer which lies inside the disk controller itself, but that's a detail) or copy on write filesystems like zfs/btrfs etc (although AFAIK they rely on a disk interface which is compatible to a rotating disk). That's to say that solid state storage is not really just persistent ram where you can apply the same datastructures and procedures you would use in core. Future technologies might be different and trim down these differences so that you could really have huge amount of super fast word addressable random memory access, where nothing can be lost even in case of power failure. But, even assuming that this might be possible, it's possible that later there will be yet another technology with even better storage density/ cost but which will introduce back some of the complications. So, it's understandable why you want to keep some abstractions, so that you can easily replace the underlying technologies and get most of the benefits.

ithkuil 14y ago

do you mean filesystems as the hierarchical way to organize stuff or the filesystem implementation that ensures that data remains persisted also in the event of unflushed writes in case of crash/poweroff etc ?

spitfire 14y ago
Both, but much more the second. disks and filesystems as a weird, separate appendage hanging off the side of a computer are conceptually a weak idea. Once you've unified your address space - stable storage is in the same space as unstable storage, then your entire world changes. The trick then becomes, how do you represent objects (Hint: Others have already tread this ground, see AS/400).
- ithkuil 14y ago
  Although many of the problems (i.e. seek time) of rotating disks are overcome by solid state persistent memory, you still need special datastructures to ensure that: a) data is buffered during write and that a power failure won't leave the storage in an inconsistent state b) blocks to be overwritten are reallocated and erased in background (you cannot simply overwrite a flash block before erasing it) c) the used datastructures (trees etc) are optimized for the size of the flash block d) gracefully handle block corruption Since it should be possible to remap blocks (either because of (b) or corruption (d)) it's common to have a logical block remapping layer somewhere in the (disk) controller. At this point classical filesystem algorithms and datastructure can easily solve the remaining problems (consistency with journaling and block optimized access like on rotating disks). Of course, there is another approach for solving (b): see http://en.wikipedia.org/wiki/Log-structured_file_system http://en.wikipedia.org/wiki/Log-structured_file_system (actually, log structured filesystem technique can be used to implement the block remapping within the ssd compatibility layer which lies inside the disk controller itself, but that's a detail) or copy on write filesystems like zfs/btrfs etc (although AFAIK they rely on a disk interface which is compatible to a rotating disk). That's to say that solid state storage is not really just persistent ram where you can apply the same datastructures and procedures you would use in core. Future technologies might be different and trim down these differences so that you could really have huge amount of super fast word addressable random memory access, where nothing can be lost even in case of power failure. But, even assuming that this might be possible, it's possible that later there will be yet another technology with even better storage density/ cost but which will introduce back some of the complications. So, it's understandable why you want to keep some abstractions, so that you can easily replace the underlying technologies and get most of the benefits.