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

H

hajime

macrumors 604
Original poster
Jul 23, 2007
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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.
 
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.
 
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.
 
maflynn said:
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.
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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.
 
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.
 
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.
 
maflynn said:
When I say slower, I mean plugging a drive in externally will be slower then the internal drive - nothing more
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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.
 
casperes1996 said:
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.
Click to expand...
So are you saying plugging in an external drive will be just as fast?
 
maflynn said:
So are you saying plugging in an external drive will be just as fast?
Click to expand...


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.
 
casperes1996 said:
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.
Click to expand...

What kind of SSD Apple uses on the MBP 2017? Are they NVMe? Do you know the brand and model numbers?
 
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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?
 
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.....
 
hajime said:
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?
Click to expand...

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.

Regime2008 said:
Why would the be an external bus that can handle higher bandwidth than the internal?
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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
 
casperes1996 said:
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
Click to expand...

Pauses on MBP 2017 13" model during the loading stage of system reboot.
 
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