Can external SSD be as fast as or even faster than internal SSD?

Discussion in 'Buying Tips and Advice' started by hajime, May 26, 2018.

  1. hajime macrumors 601

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    #1
    Hello, I have not used Thunderbolt before. With Thunderbolt 3 /UCB-C, can external SSD be faster or even as fast as the internal one that came with the MBP 2017? Will having an external TS3+ in between the MBP and the external SSD slow things down? What products do you recommend?

    Also, can such external SSD be used as a boot drive? For example, I install Windows and/or Linux on the external SSD and boot to any of these OS from the external drive.
     
  2. casperes1996 macrumors 68040

    casperes1996

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    #2
    Considering how insanely fast the internal SSDs are, you'll struggle finding a faster SSD for external use. But is it theoretically possible to have a faster SSD connected over TB3 and get faster speeds? Yes. It is.

    And yes, you can use it as a boot drive. I've booted macOS off of an external SSD a lot for beta testing.
     
  3. maflynn Moderator

    maflynn

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    #3
    No, it will be slower, but I'm not sure how noticable it will be. I run my iMac off an external SSD and its fast enough for my needs. I suppose it depends on usage.
     
  4. casperes1996 macrumors 68040

    casperes1996

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    #4
    When you say slower, I assume you mean with the SSDs available now. Because I'm fairly certain that the TB3 connection would not severely hinder performance if the drive itself was much faster, so in future, if we see a drive that hits 10GB/s, the TB3 drive would indeed be faster than the internal one. There may be added latency to the TB connection, but throughput should be off the hooks, since TB3 can do around 40GB/s if I recall correctly.
     
  5. Darmok N Jalad macrumors 65816

    Darmok N Jalad

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    #5
    I’ve plugged a SATA SSD into a USB 3.1 adapter into my iMac and speed tested it. I believe I got around 400MB/s read/write, which would be more than fast enough for running an OS. It doesn’t compare to the internal blade SSD, but for most tasks, you’d never notice. I think they make Thunderbolt blade SSD enclosures that are really fast, but you’ll drop a lot of money on such a setup.
     
  6. maflynn Moderator

    maflynn

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    #6
    When I say slower, I mean plugging a drive in externally will be slower then the internal drive - nothing more
     
  7. hajime thread starter macrumors 601

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    #7
    The thing is on my MBP 2010, I had a 1TB drive. Half for Mac OS and half for Windows. Both are pretty full. I added another 1TB drive and install Linux on it.

    With those thin MBP, I will not be able to install two SSD in it. I guess choosing the 2TB option from Apple could be very expensive. So I am considering to move some of the stuffs to external SSD if I do get the 2018 MBP.
     
  8. casperes1996 macrumors 68040

    casperes1996

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    #8
    Thunderbolt 3 has the same bandwidth as 4x PCIe 3.0. Now there is some overhead to using Thunderbolt compared to PCIe, with added latency and signal handling overhead, but the throughput is really high with TB3, and no SSD on the market yet can saturate that connection. If in the future we get drives that can, they will indeed be faster than the internal one. Now again, there will probably be a bit of added latency and a few CPU cycles spent handling the connection, but the bandwidth will be greater.
     
  9. maflynn Moderator

    maflynn

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    #9
    So are you saying plugging in an external drive will be just as fast?
     
  10. casperes1996 macrumors 68040

    casperes1996

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    #10

    I'm saying it can be. Not that it will be. Think of it this way, if you can run external GPUs, there's no reason you wouldn't be able to have insanely fast external SSDs, when we have connections capable of that kind of bandwidth. The SSDs Apple use are really high end, so it's hard to really find any better, but imagine a few years from now we take the 5th generation of Octane or whatever, and put it in an external PCIe enclosure and hook it up with Thunderbolt, well, I assume you that'll be faster than the internal drives of today.
     
  11. hajime thread starter macrumors 601

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    What kind of SSD Apple uses on the MBP 2017? Are they NVMe? Do you know the brand and model numbers?
     
  12. Darmok N Jalad macrumors 65816

    Darmok N Jalad

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    #12
  13. hajime thread starter macrumors 601

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    #13
    I put a Samsung EVO 850 (SATA III ?) HD in my MBP 2010 17". In my less than two-week use of the MBP 2017, I did not see noticeable improvement in storage speed performance. Especially in rebooting the machine, the MBP 2017 did not seem to be faster than my MBP 2010. I saw long pauses each time the system was loaded. How come?
     
  14. Regime2008 Suspended

    Regime2008

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    #14
    Why would the be an external bus that can handle higher bandwidth than the internal?
     
  15. Ifti macrumors 68000

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    #15
    I have an OWC Thunderblade v4 which connects via TB3. This has 4 NVMe SSDs in RAID and it reaches 2800MB/s - probably around the speed of an internal SSD.....
     
  16. casperes1996 macrumors 68040

    casperes1996

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    #16
    What system is it that you're talking about pauses on?

    I'd wager you not seeing the speed difference, is more down to your workflow not benefitting much from the extra speed beyond a certain point.

    That's not the point though. The internal bus isn't fully saturated at all. PCIe can handle much, much more data than contemporary SSDs. Thunderbolt 3 ≈ PCIe 3.0 x4, which is what the internal drive uses. Now going over an external connection does add a bit of processing and latency overhead, bit since the bus isn't at all saturated yet, the faster drives we'll get in the future could get closer to, or even fully saturate the connection, and thus, using that drive on a TB3 connection would be faster than the factory shipped SSD
     
  17. hajime thread starter macrumors 601

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    Pauses on MBP 2017 13" model during the loading stage of system reboot.
     
  18. casperes1996 macrumors 68040

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    #18

    Do you mean after the system is loaded, or do you mean that the progress bar seems to pause a bit?
     
  19. hajime thread starter macrumors 601

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    #19
    Progress bar with the big Apple logo in the middle. We see that also when you turn on the machine.
     
  20. casperes1996 macrumors 68040

    casperes1996

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    #20

    In that case no worries. It's common.
     
  21. hajime thread starter macrumors 601

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    #21
    Then why the MBP 2017 with better CPU and SSD are as slow as the old 2010 MBP during boot up?
     
  22. casperes1996 macrumors 68040

    casperes1996

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    #22

    There are many things in play during a boot-up process. The bottleneck at this point may be initialising other chips on the logic board
     
  23. hajime thread starter macrumors 601

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    Does the TB has anything to do with the delay?
     
  24. casperes1996 macrumors 68040

    casperes1996

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    #24

    It probably adds to the initialisation process, but the process bar would hang for a tiny bit regardless. It's not that the process is delayed or anything, it''s just the visual presentation of the progress
     

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