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Best way of connecting an external drive via USB-C


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Old 07-12-2016, 17:13
tdenson
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I've got a new MacBook Pro with USB-C and am looking for the way of getting the best performance with an external SSD. I have bought an external enclosure that has a USB-C connector, but when I connect it to my MacBook I get (relatively) mediocre performance - a couple of minutes to transfer a 6GB file, compared with 6 seconds to transfer the same file from one place to another on the internal drive. Now obviously I'm not expecting to match the internal bus, but I thought I would be able to do better. Do I need a Thunderbolt external drive for example ?
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Old 07-12-2016, 17:23
chrisjr
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I've got a new MacBook Pro with USB-C and am looking for the way of getting the best performance with an external SSD. I have bought an external enclosure that has a USB-C connector, but when I connect it to my MacBook I get (relatively) mediocre performance - a couple of minutes to transfer a 6GB file, compared with 6 seconds to transfer the same file from one place to another on the internal drive. Now obviously I'm not expecting to match the internal bus, but I thought I would be able to do better. Do I need a Thunderbolt external drive for example ?
When you did the transfer on the internal drive did you create a second copy of the file or simply "move" it from one folder to another.

If you "moved" it then the file very likely stayed where it was physically on the drive and only the entries in the index files of the disk were changed.
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Old 07-12-2016, 18:01
Stig
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I'm guessing it's a problem with the enclosure interface. USB 3.1 gen 1 is capable of 5Gbps and gen 2 is 10Mbps.
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Old 07-12-2016, 23:01
tdenson
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When you did the transfer on the internal drive did you create a second copy of the file or simply "move" it from one folder to another.

If you "moved" it then the file very likely stayed where it was physically on the drive and only the entries in the index files of the disk were changed.
Yes, I understand the difference between copying and moving. I duplicated it.
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Old 08-12-2016, 18:37
tdenson
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I've been doing a bit of reading around and it seems the key issue is whether the drive has "UASP" support. This is a SCSI protocol. On the Mac one should see it as a SCSI peripheral in the About my Mac section instead of a USB device. According to the spec of the drive enclosure I bought it specifically mentions UASP, however I don't see it as such on the Mac which just sees it as USB. Anyone know what I am missing here ?
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Old 09-12-2016, 22:45
tdenson
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This is all very confusing. I have bought a Samsung external SSD and connected it via the supplied USB-C to USB/A cable and then via a USB-C hub to the MacBook. I now can transfer my 5GB file in 15 seconds instead of a couple of minutes. However, using the same enclosure connected directly to the MacBook with a USB-C to USB-C cable I am back to the slow transfer time.
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Old 10-12-2016, 00:16
Roush
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There are different flavours of Type-C USB cables that support different speeds and modes of operation.

Are you by any chance using the charge cable that Apple supply with the MBP for connecting Type-C USB devices directly? If so, that would explain the speeds you're seeing. The charge cable only supports data transfer at USB 2.0 speeds, at which 6GB in a couple of minutes would sound about right.

You need to be using a USB 3.1 SuperSpeed+ cable to get the maximum possible speeds.

UAS drives will still show as USB devices. Only true parallel SCSI devices (rare these days) will show as SCSI

To confirm UAS operation you need to be looking for the UAS kext to be listed as 'Yes' in the loaded column in the Software > Extensions list of System Information after a UAS-enabled drive has been connected.

The kext in question will either be called IOUSBAttachedSCSI or IOUSBMassStorageUASDriver
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Old 10-12-2016, 18:25
tdenson
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There are different flavours of Type-C USB cables that support different speeds and modes of operation.

Are you by any chance using the charge cable that Apple supply with the MBP for connecting Type-C USB devices directly? If so, that would explain the speeds you're seeing. The charge cable only supports data transfer at USB 2.0 speeds, at which 6GB in a couple of minutes would sound about right.

You need to be using a USB 3.1 SuperSpeed+ cable to get the maximum possible speeds.

UAS drives will still show as USB devices. Only true parallel SCSI devices (rare these days) will show as SCSI

To confirm UAS operation you need to be looking for the UAS kext to be listed as 'Yes' in the loaded column in the Software > Extensions list of System Information after a UAS-enabled drive has been connected.

The kext in question will either be called IOUSBAttachedSCSI or IOUSBMassStorageUASDriver
Very helpful thanks.
I can see the IOUSBAttachedSCSI but Loaded is showing as no.

I yam using the USB-C to USB-A cable that came with the Samsung drive, but obviously I am also having to go via another USB to USB-C adaptor to connect to the MacBook. I guess that is where the problem lies. But what a minefield.
I'm getting a decent throughput as is, but it would be nice to know how to select a cable that will work as UASP.
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