iPad USB-C File copy speed seems really slow

Fry-man22

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Original poster
Nov 25, 2007
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On my 2018 iPad Pro I'm seeing pretty slow speeds for a USB-C setup and all SSDs.

I copied an 88GB file from one SSD to another through a USB gen2 hub. This took 45 minutes on the iPad. The exact same setup did the copy in 3.5 minutes on my MacBook Pro.

I realize this is a beta, but that is an order of magnitude slower than I was expecting. Just curious what speeds others are seeing when interacting with external devices.

Maybe copy directly to the iPad is faster? Interested to hear other experiences.
 
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Dwalls90

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Feb 5, 2009
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On my 2018 iPad Pro I'm seeing pretty slow speeds for a USB-C setup and all SSDs.

I copied an 88GB file from one SSD to another through a USB gen2 hub. This took 45 minutes on the iPad. The exact same setup did the copy in 3.5 minutes on my MacBook Pro.

I realize this is a beta, but that is an order of magnitude slower than I was expecting. Just curious what speeds others are seeing when interacting with external devices.

Maybe copy directly to the iPad is faster? Interested to hear other experiences.
The Storage speeds and controller on your MacBook Pro are much faster than the iPad. You’ll never see the iPad matching MacBook Pro speeds, though maybe it’ll improve throughout the beta process.
 

Fry-man22

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Nov 25, 2007
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The Storage speeds and controller on your MacBook Pro are much faster than the iPad. You’ll never see the iPad matching MacBook Pro speeds, though maybe it’ll improve throughout the beta process.
Not sure about the controller being an issue, or about that statement being strictly true. Perf Tests lists the write speed on my internal storage to be 550MB/s and previous models read at 1200MB/s so the controller can at least do that.

https://blog.fosketts.net/2015/09/28/apple-packs-pcie-ssd-alongside-pc-fast-cpu-and-graphics-in-iphone-6s-and-ipad-pro/

That says they have had PCI-E for everything for a while, so I assume the USB controller is hooked to PCI-E.

Anyway, I'm seeing between USB 2.0 and Firewire 800 speeds. Regardless of the controller, modern hardware has passed that at any level. I'm just wanting to know if it's something specific to my setup or if everyone sees this level of performance (or lack of rather).
 
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Dwalls90

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Feb 5, 2009
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Not sure about the controller being an issue, or about that statement being strictly true. Perf Tests lists the write speed on my internal storage to be 550MB/s and previous models read at 1200MB/s so the controller can at least do that.

https://blog.fosketts.net/2015/09/28/apple-packs-pcie-ssd-alongside-pc-fast-cpu-and-graphics-in-iphone-6s-and-ipad-pro/

That says they have had PCI-E for everything for a while, so I assume the USB controller is hooked to PCI-E.

Anyway, I'm seeing between USB 2.0 and Firewire 800 speeds. Regardless of the controller, modern hardware has passed that at any level. I'm just wanting to know if it's something specific to my setup or if everyone sees this level of performance (or lack of rather).
Check the below out:

https://forums.macrumors.com/threads/ipad-pro-10-5-12-9-ssd-storage-speed-test-64-256-512gb.2105666/

Compare that with MacBook Pro speeds:

https://www.macrumors.com/2018/07/13/2018-macbook-pro-fastest-laptop-ssd-ever/
 

T-Bob

macrumors 6502a
Oct 23, 2013
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On my 2018 iPad Pro I'm seeing pretty slow speeds for a USB-C setup and all SSDs.

I copied an 88GB file from one SSD to another through a USB gen2 hub. This took 45 minutes on the iPad. The exact same setup did the copy in 3.5 minutes on my MacBook Pro.

I realize this is a beta, but that is an order of magnitude slower than I was expecting. Just curious what speeds others are seeing when interacting with external devices.

Maybe copy directly to the iPad is faster? Interested to hear other experiences.
Silly question, but just in case. You are using a usb3+ rated cable on iPad? One that comes with it will be slower. Always use TB3 cable when doing large transfers myself.
 

jimmyjoy

macrumors member
Sep 20, 2012
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I’m not sure if this is related or not but I’m having a bit of an issue.

Last week I bought a Fuji XT3 which uses SD cars. I purchased the Sandisk USB C card reader and had a really good experience using it to import photos into the photo app.

After installing iOS13 it now barely works. Sometimes it pops up in the photos app but says there is nothing to import. Once it came up with photos but the transfer speed was horrendous and most of the time it doesn’t pop up at all. I can see the device in the files app labelled ‘errorname’ and can see the files but I can’t do anything with them. I’m unsure if it’s a fault card reader or iOS13 that’s the issue.
 

Fry-man22

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Original poster
Nov 25, 2007
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Yes, those are comparing the internal SSD throughput. I'm not debating that the flash in the MacBooks is faster than the internal flash in the iPad. Those are the built in SSD numbers, not the numbers that max out the controller.

I am debating, and disagreeing with, the idea that the speeds I'm seeing have anything to do with a controller limitation. Let's just take the read of 1200MB/s that you posted is the max throughput. I'm using external USB C SSD that have a read/write of around 500MB/s so that max is greater than these anyway. If I was getting 500 write and 1200 read this post would not exist.

Silly question, but just in case. You are using a usb3+ rated cable on iPad? One that comes with it will be slower. Always use TB3 cable when doing large transfers myself.
I'm using the cables that shipped with the 512GB Samsung T3 and the 2TB SanDisk Extreme Portable that are being used as the source and target disks respectively. Also the fact that the MacBook Pro can get the transfer done in 3 min means the setup has the hardware potential to perform at the expected level.
 
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T-Bob

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Oct 23, 2013
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From my limited searching there doesn't seem to be a large amount of testing out there. You can see videos like:
that show differences between usb 2 and 3 speeds. But they're also doing a simple copy from or to an external device, you are actually transferring between two devices it seems?

Try just copying data from one ssd to the pad or vice versa, that should be significantly faster. Not sure a complex copy operation with the iPad as a hub will be able to leverage full bus speeds.
 

Fry-man22

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Original poster
Nov 25, 2007
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Try just copying data from one ssd to the pad or vice versa, that should be significantly faster. Not sure a complex copy operation with the iPad as a hub will be able to leverage full bus speeds.
Well it appears the the process of writing OUT to the external is the slowest part of the process.

Copying this to the internal storage from the SSD I get about 10 min, that's fine and I can live with that kind of throughput.

Copying this to the SSD from the internal storage, now things get slow again - 44 minutes. In fact it gets exactly as slow as it was copying from SSD to SSD using the hub.

It seems that the copy out to the SSD is going to be slow right now, but there also appears to be no lag introduced by the iPad as a bridge because Internal->SSD is the same speed as SSD->SSD.

Again, I know this is going to get better during the beta, I was just wanting to confirm that I was seeing was the expected behavior for the current version.
 
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zorinlynx

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May 31, 2007
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I wouldn't be surprised if there are performance issues with iOS 13 USB drive access, for the simple reason that they're re-implementing the entire USB storage and filesystem stack in user mode for security reasons as part of it all.

In MacOS, USB storage and filesystems are handled in the kernel. iOS 13 is doing it all in user mode. For those familiar with it, it's analogous to the FUSE filesystem. It will be slow until they optimize it some. This may apply especially to *writes*, especially if they're done synchronously to protect against someone unplugging the storage unexpectedly.

Regardless of all this, performance should improve moving forward. I'm just happy to be getting this capability at all! :)
 
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