Exactly How Fast are These New MBP SSDs

Discussion in 'MacBook Pro' started by fisherman188, Nov 11, 2016.

  1. fisherman188 macrumors member

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    Oct 21, 2014
    #1
    So in the last couple years, especially for Apple, Solid State Drives have made leaps and bounds in terms of read write speed. Even the 2015 MBP had a very fast drive and the 2016 (on paper) runs circles around even it.

    I've done some searching and can't find any tests or results on the subject but I'm wondering: how does a swap/cache/paging file (essentially virtual RAM) on these new speedy SSDs compare to physical RAM? With the 16 GB limit of DDR3 RAM can I add say 40 extra gig of Virtual RAM and see a 15% drop performance compared to all physical or what? If these SSDs can get within 10% of physical RAM the 16 GB limit would be completely doable. RAM speeds are always increasing too so with the LPDDR3 at a certain megahertz, how much are we losing compared to DDR4?

    Has anyone seen or tested things like this with the 2015 MBP or other SSDs?
     
  2. New_Mac_Smell, Nov 11, 2016
    Last edited: Nov 11, 2016

    New_Mac_Smell macrumors 65816

    New_Mac_Smell

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    #2
    Eventually SSDs will catch up to RAM access speeds and make it irrelevant for the caching they offer, but we're a way off. I think the new SSDs are about 60x slower than RAM (Old HDDs are hundreds). And there was a report I read a few days ago that I couldn't find for you that talked about a new standard coming that might be closer to 30-40x (Quoting from memory).

    If things continue, you could see it in 10 years that you just use a special SSD instead of RAM and can have however much you need. But until there is a market for several hundred GB of RAM, it won't likely happen soon. But we'll hopefully get a nice stop gap period of being able to have sufficient RAM, and something like an l5 cache system.

    I'll try find the article and post it if I can, sure someone will be able to find it though.

    Edit: Here's one http://www.computerworld.com/articl...pro-could-sport-intels-new-3d-xpoint-ssd.html intel optane stuff.
     
  3. fisherman188 thread starter macrumors member

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    Oct 21, 2014
    #3
    Oh I was just throwing out percentages I didnt know at all. I just didn't have any data on it and was hoping to glean some information. Thanks for your input.

    I'm hoping to do some real world testing on it to see exactly how much performance decrease I see and if it's managable. I'm hoping to be able to boot and use 15-20 virtual Cisco Nexus routers in their Ubuntu VM. There's a huge difference in boot time and the operation of them with a swap file on slower SSDs but this should make up the gap. I have no doubt that a 50 -100GB cache file in Photoshop will be more than sufficient to replace physical RAM but we will just have to see on the routers.
     
  4. Toutou macrumors 6502a

    Toutou

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    #4
    Not exactly, both the speed and the LATENCY are major factors. SSDs are getting really fast these days but the difference in latency between the RAM and an SSD is massive.
    You're right that a day may come when the main memory (RAM at this time) just fuses with the external memory (HDDs and SSDs) but that would, in my opinion, require a major architectural change, e.g. the introduction of several new cache levels that would gradually become the new multi-level main memory, and a complete overhaul of mechanisms used to handle it (virtual memory, segmentation, paging)

    The concept of fast main memory and slow permanent storage is just too old and well understood.
     
  5. jackoatmon macrumors 6502a

    jackoatmon

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    Sep 15, 2011
    #5
    I don't think you'll ever truly see storage memory and RAM fuse.

    Because in reality there are many levels of memory. From what I understand, even a CPU has a bunch of little RAM-like features (L1 cache, L2 cache) that work like an even smaller, even faster version of RAM. And the GPU has it's own vRAM, which for its purposes is quite a bit better than just having access to extra system RAM.

    It's kinda like, you have cups, pitchers, buckets and pools. They all hold water. But different amounts for different lengths of time. More temporary storage options is kinda better in a way, not worse.

    I could imagine a future where there are even more levels of RAM, not less. But who knows maybe some quantum computing thing will happen and we'll all be like "ho ho ho, RAM, what a silly concept!"
     
  6. New_Mac_Smell macrumors 65816

    New_Mac_Smell

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    #6
    Yeah RAM acts like l4, just because HDDs are slow. But if SSDs ever got to the same speed there shouldn't be a need for it (However unlikely as RAM will probably always outpace it).

    To be fair, I remember like 15-20 years ago seeing people building HDDs out of RAM chips, and thought it was pretty far out. Yet here we are with SSDs and flash drives. So who knows!
     
  7. jackoatmon macrumors 6502a

    jackoatmon

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    #7
    I guess what I mean is, we could make all the windows on our houses out of diamonds. But why would we?
     
  8. New_Mac_Smell macrumors 65816

    New_Mac_Smell

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    #8
    Because of cost and physics?
     
  9. leman, Nov 11, 2016
    Last edited: Nov 11, 2016

    leman macrumors 604

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    #9
    Keep in mind that those SSDs have maximal sustained bandwidth of 3GB/s (which is about 1/10 of what 2133Ghz DDR RAM can do), the random reads are slower and there is filesystem overhead on top of it. So I think about 1/50-1/30 of RAM speeds is the best one can get in a real-world scenario.
    --- Post Merged, Nov 11, 2016 ---
    Once we have cheap, fast persistent storage, volatile RAM will become unnecessary as a concept. Even now, RAM kind of works as a cache to the SSD/HDD — from the perspective of the OS, all memory is allocated as files on a disk and is backed by the disk storage (even though normal heap memory usually never ends up on the disk itself). If the SSDs get as fast as RAM, we simply won't need RAM anymore. Of course, the CPU caches will still likely to be necessary for a long long time, unless the main memory becomes INSANELY fast.

    P.S. In simple terms, at some point its likely that what we call RAM and disk will fuse into a single persistent RAM (random access memory) unit. There is already tech in development that blurs the distinction between DDR and SSDs (e.g. Intel's Optane).
     
  10. xmonkey macrumors 6502a

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    CA
    #10
    If Intel can deliver on their promises for Optane/X-Point we're going to see some pretty great things in the future. Big if, though.
     

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