Cable Compatibility Confusion: USB-C to USB-A; Transfer Speeds (LaCie d2 Professional External HD)

cubbie5150

macrumors 6502a
Original poster
Mar 4, 2007
573
107
I have been throwing money at a stupid issue and asking about it now just makes me feel more stupid, but here goes...

I have the LaCie d2 Professional external hard drive that has 1x USB 3.1 Gen 1 (USB Type-C) interface/single port on the back. It also comes with 2 short cables: (1) a USB 3.1 (5 Gb/s), type C to type C; and (2) a USB 3.0, type C to Type A.

As I own a 2014 MBP that has two Thunderbolt 2 (mini DisplayPorts) and 2 USB 3.0 ports, I initially used the 2nd cable, and based on the transfer (according to iStat) from both my MBP internal SSD and another external hard drive (via BOTH Thunderbolt 2 and USB 3.0), I was getting peak transfer rates of up to 240 MB/s.

However, it was inconvenient using such a short cable so I looked for longer options. I'll spare all the boring details but I've tried:
--a 6 ft Amazon Basics USB 3.1, gen 1, type C to type C + type A to type C adapter (rated as capable of USB 3.1, gen 2 5 Gb/s);
--a 6 ft Monoprice Thunderbolt 3, 20 Gb/s, type C to type C + a different type A to type C adapter;
--and finally a 6 ft Monoprice USB 3.0, type C to type A cable

The consistent thing is with all three of those setups, I can only achieve max 40 MB/s transfer rates.

****in case you're wondering why I first tried the top 2 options of type C to type C cables + type C to type A adapters, I figured I'll soon be upgrading to a new MBP, so figured I'd go type C cables now

What gives? I thought cables/adapters were backwards compatible, and even if not, why is the last cable tried (the USB 3.0 type C to type A) having the same result?

Help please? I'm tired of throwing more annoying bits of $$ at this.
 

cubbie5150

macrumors 6502a
Original poster
Mar 4, 2007
573
107
did you try measuring transfer speed with other apps
I have not, no. But, based on how painstakingly long it actually took to transfer various files of various number and sizes using those three cable setups noted in the OP, compared to how blazing fast it was when using the LaCie (short) USB 3 cable, I honestly did witness a huge, obvious speed disparity.
 

Fishrrman

macrumors P6
Feb 20, 2009
18,261
6,129
For an external SSD connected via USB3, you should be seeing READ speeds of 420-430MBps, and WRITE speeds in the 330-360MBps range (this depends on the drive manufacturer, enclosure, etc.).
 

cubbie5150

macrumors 6502a
Original poster
Mar 4, 2007
573
107
Yep, 7200 rpm HD. Again, when using the LaCie-supplied (short) USB 3.0 type to type C cable between the HD and my 2014 MBP, I got peak transfer rates of 235 to 240 MB/s. Using any of the other cable setups, I get max peak transfer of 35 to 40 MB/s.

I tested several different file transfers from my MBP internal SSD to the LaCie HD. Per Finder, expected file transfer time when using the LaCie cable was 5 to 6 times less tha when using any of the other cable set-ups.

I'm really confused by this, and mostly just aggravated that I've spent ~$75 on cables for this one stupid use, and none of them work worth a crap. Ugh.
 

Fishrrman

macrumors P6
Feb 20, 2009
18,261
6,129
"Again, when using the LaCie-supplied (short) USB 3.0 type to type C cable between the HD and my 2014 MBP, I got peak transfer rates of 235 to 240 MB/s. Using any of the other cable setups, I get max peak transfer of 35 to 40 MB/s."

Use what works for you.
Don't use what doesn't.
 

cubbie5150

macrumors 6502a
Original poster
Mar 4, 2007
573
107
Ugh...I get that but the provided cable is only 28" long end to end. I just don't understand why no non-LaCie cable has worked work a damn thus far. I appreciate you taking the time to respond, but it isn't particularity helpful in this case. I know the LaCie cable works; I don't need to be told that. I don't get why it's hard to understand I want/need to use a longer cable.
 

jaytv111

macrumors regular
Oct 25, 2007
237
72
It sounds like it's stuck with USB 2.0 speeds with the other cables. Can you find the device in About This Mac->System Report->USB and see what speeds it's getting? It appears that your adapters or cables are not running at 3.0 speeds.