Ian Smith wrote:> On Mon, 2 Jan 2017 11:27:49 +0300, Marat N.Afanasyev wrote:
> > I wonder is there a speed limit on usb 3.0? I've bought
> >
> > ugen0.4: <SanDisk> at usbus0
> > umass2 on uhub7
> > umass2: <SanDisk Extreme, class 0/0, rev 2.10/0.10, addr 4> on
usbus0
> > da2 at umass-sim2 bus 2 scbus9 target 0 lun 0
> > da2: <SanDisk Extreme 0001> Removable Direct Access SPC-4 SCSI
device
> > da2: Serial Number AA010808161609220143
> > da2: 40.000MB/s transfers
> > da2: 59840MB (122552320 512 byte sectors)
> > da2: quirks=0x2<NO_6_BYTE>
> >
> > that claims 'Up to 245 MBytes/sec read speed'
> >
> > and dd shows:
> >
> > % dd if=/dev/da2 of=/dev/null bs=1m count=1000
> > 1000+0 records in
> > 1000+0 records out
> > 1048576000 bytes transferred in 25.688997 secs (40818098 bytes/sec)
> >
> > why we have such a limit?
>
> Seems you've plugged it into a USB 2 port, not USB 3
>
> At least you're getting full USB 2 performance (40MB/s)
>
> Check if you have one or more USB 3 ports with 'dmesg | grep xhci'
>
> cheers, Ian
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afair, single usb 2.0 device can be as fast as 240 Mbits/sec, not 320
Mbits/sec:
% dd if=/dev/da2 of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 34.026227 secs (30816699 bytes/sec)
it's the same drive in usb 2.0 port
And I do have usb 3.0:
% grep xhci /var/run/dmesg.boot
xhci0: <XHCI (generic) USB 3.0 controller> mem 0xfeaf8000-0xfeafffff irq
17 at device 0.0 on pci5
xhci0: 64 bytes context size, 64-bit DMA
usbus0 on xhci0
xhci0: <XHCI (generic) USB 3.0 controller> mem 0xfeaf8000-0xfeafffff irq
17 at device 0.0 on pci5
xhci0: 64 bytes context size, 64-bit DMA
usbus0 on xhci0
and I tried this thumb drive is in usb 3.0 port first, of course.
--
SY, Marat
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