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 _______________________________________________ freebsd-stable@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "freebsd-stable-unsubscr...@freebsd.org"
