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? -- SY, Marat -------------- next part -------------- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 3805 bytes Desc: S/MIME Cryptographic Signature URL: <http://lists.freebsd.org/pipermail/freebsd-stable/attachments/20170102/df347045/attachment.bin>
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
On Mon, Jan 02, 2017 at 11:27:49AM +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'I don't think the speed reported by the SCSI layer (CAM) is correct for USB, although it seems from an experiment here that if you plug a USB3 drive into a USB2 port it reports "40.000MB/s transfers" and on a USB3 port it reports "400.000MB/s transfers". SCSI doesn't really have any direct mapping to the USB speeds so I suspect the USB stack uses the closest value. The tests I did were with 10.3. Other releases may behave differently. Check with usbconfig what the negotiated USB speed is (the "spd=" value with the Mbps or Gbps value in brackets afterwards) FULL = USB1 HIGH = USB2 SUPER = USB3 Regards, Gary