5 ms·

Wouldn't that waste a whole lot of CPU cycles? Granted a lot of CPU cycles are just waiting for disk anyway, but directly managing flash would probably distract

Wouldn't that waste a whole lot of CPU cycles? Granted a lot of CPU cycles are just waiting for disk anyway, but directly managing flash would probably distract the CPU from processing data for at least some workloads.

pedrocr 12y ago
The same argument is used for TCP offload to NICs and from what I've seen it ends up being a bad idea because host CPUs advance much faster than the ones you put in your SSD/NIC/etc. Add to that the fact that you are almost surely leaving optimizations on the table from separating the two layers and I'd very much doubt there would be much performance loss. And I'd gladly take a performance hit if it meant SSDs become a safe commodity product like hard drives mostly are vs the current situation where a crappy product may very well erase all its data on an unclean shutdown. Manufacturers don't want this of course because there's more margin to be had with the current stuff. Maybe some low end manufacturers could start to implement low-level flash access and Linux using it for the situation to change.
- baruch 12y ago
  The big pain in such an endeavor is the high cost of an hardware company and the low quantity and the long time it will take to build an ecosystem around such an offering. I'd buy one or a few but beyond the tinkerers there aren't going to be many buyers. Unless someone of the Google/Facebook clubs will decide it is in their best interest to have such a thing and to enable it to be sold to others as well it is not that likely to happen.
- ghshephard 12y ago
  But isn't it the case that Hard Drives have firmware managing most of the "on-drive" behavior?
  - pedrocr 12y ago
    They manage the hardware bits (rotation speed, head movement, etc) but they don't present much of an abstraction layer over that (they do remap bad blocks). The SSD equivalent would be a firmware that just presents the block structure with wear counters per block and possibly does the read-modify-write dance for writes smaller than a block and remaps broken blocks to a few it keeps hidden. All the other wear leveling stuff it can just let the OS handle.

pedrocr 12y ago

The same argument is used for TCP offload to NICs and from what I've seen it ends up being a bad idea because host CPUs advance much faster than the ones you put in your SSD/NIC/etc. Add to that the fact that you are almost surely leaving optimizations on the table from separating the two layers and I'd very much doubt there would be much performance loss. And I'd gladly take a performance hit if it meant SSDs become a safe commodity product like hard drives mostly are vs the current situation where a crappy product may very well erase all its data on an unclean shutdown. Manufacturers don't want this of course because there's more margin to be had with the current stuff. Maybe some low end manufacturers could start to implement low-level flash access and Linux using it for the situation to change.

baruch 12y ago
The big pain in such an endeavor is the high cost of an hardware company and the low quantity and the long time it will take to build an ecosystem around such an offering. I'd buy one or a few but beyond the tinkerers there aren't going to be many buyers. Unless someone of the Google/Facebook clubs will decide it is in their best interest to have such a thing and to enable it to be sold to others as well it is not that likely to happen.
ghshephard 12y ago
But isn't it the case that Hard Drives have firmware managing most of the "on-drive" behavior?
- pedrocr 12y ago
  They manage the hardware bits (rotation speed, head movement, etc) but they don't present much of an abstraction layer over that (they do remap bad blocks). The SSD equivalent would be a firmware that just presents the block structure with wear counters per block and possibly does the read-modify-write dance for writes smaller than a block and remaps broken blocks to a few it keeps hidden. All the other wear leveling stuff it can just let the OS handle.