[Cialug] SSD in a DIMM

[Thomas Kula]

On Mon, Jan 05, 2015 at 06:54:22PM -0600, Matthew Nuzum wrote:
> Maybe the goal is to be able to address storage in the same way you address
> RAM. For example, if you had a 512GB SSD and 16GB of RAM it would appear as
> if you had 528GB of RAM. No different than if you have a really huge swap
> file. Then, you don't have to worry about storing to disk, you just access
> your storage from memory.
> 
> For example, memcached. Also, the memory would be nonvolatile I guess.
> 
> Presumably, the OS knows which memory is fastest and optimizes allocation
> based on that.
> 
> Pure conjecture, I really just looked at the headlines and the pictures. :-)
> 

The webpage is rather sparse on details, but if you follow a few video
links there's much better information:

- Requires a BIOS/mobo that knows what to do with the memory
- The SSD DIMM is not added to your total system memory
- Requires you to still use conventional DIMM for system memory
- A (proprietary, as of one of the videos I was watching from mid-2014)
  driver makes each SSD DIMM appear as a block device. The driver and
  mobo work together so that access to these block devices goes through
  the memory channels, instead of having to go through north bridge ->
  pcie bus -> controller -> sata/sas bus.
- Burstable (apparently) DDR3 speed, but of course, since it's backed by
  (even spiffy) SATA3 flash drives --- the magic sauce is really a DDR3
  to SATA bridge --- that won't be maintainable for long. The idea
  appears to be that with enough of these and memory access spread out
  amongst enough channels, it won't matter (or matter as much).

An interesting little device, and I'd love to play around with a machine
that has it in it. Am I scrambling to get work to buy a slew of them?
Not yet. 


-- 
Thomas L. Kula | kula at tproa.net | http://kula.tproa.net/