Laptop with USB3 in spec, USB2 in reality

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Laptop with USB3 in spec, USB2 in reality

Postby andy55 » 2020-09-27 12:55

Hello all,

I have bought refurbished DELL XPS 9550 and installed Debian Buster. According to its specification this laptop has 2 x USB3 (but USB ports are black :( )
I was trying to copy files to/from two different portable, external USB3 drives but the speed is really slow. Did some benchmark using dd:
Code: Select all
dd if=/dev/sda of=/dev/null bs=10M count=100

and it shows between 100 MB/s and 120 MB/s transfer.
Googled it but it looks like the speed doesn't match neither USB2 (a bit above ?) nor USB3 (below its nominal speed).
Can you hint me please if I am testing it wrong or right ?
andy55
 
Posts: 45
Joined: 2012-08-20 12:59

Re: Laptop with USB3 in spec, USB2 in reality

Postby p.H » 2020-09-27 13:40

It matches an average hard disk sequential speed. It is way above USB 2 high-speed capability (~40 MB/s).
p.H
 
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Re: Laptop with USB3 in spec, USB2 in reality

Postby sgosnell » 2020-09-27 14:38

I think you also need a USB3 cable to get full USB3 speeds. A regular USB2 cable can't carry the freight.
Take my advice, I'm not using it.
sgosnell
 
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Re: Laptop with USB3 in spec, USB2 in reality

Postby andy55 » 2020-09-27 19:41

The portable disk already had USB3 cable included (blue interface).
andy55
 
Posts: 45
Joined: 2012-08-20 12:59

Re: Laptop with USB3 in spec, USB2 in reality

Postby sgosnell » 2020-09-27 19:53

No matter how high the bandwidth is, the throughput may be limited by the speed of the drives, as noted above.
Take my advice, I'm not using it.
sgosnell
 
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Re: Laptop with USB3 in spec, USB2 in reality

Postby andy55 » 2020-09-27 20:16

Thanks a lot guys !
andy55
 
Posts: 45
Joined: 2012-08-20 12:59


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