I compare the data transfer rate on FreeBSD 11.2 (same on 11.1) with Debian Stretch (Raspbian) on the same hardware: with "dd if=/dev/da0 of=/dev/null bs=32k" On FreeBSD, I get approx 13MB/s On Debian, I get approx 37MB/s My hardware is the Raspberry PI2 B (Cortex-A7) and a 2TB Intenso External USB Disk. Here is some information from /var/log/messages: kernel: ugen0.4: <Intenso External USB 3.0> at usbus0 kernel: umass0 kernel: on uhub1 kernel: umass0: <Intenso External USB 3.0, class 0/0, rev 2.10/3.07, addr 4> on usbus0 kernel: da0 at umass-sim0 bus 0 scbus0 target 0 lun 0 Aug 31 18:09:12 rpiBackup kernel: da0: <Intenso External USB 3.0 5438> Fixed Direct Access SPC-4 SCSI device kernel: da0: Serial Number 20161117015346 kernel: da0: 40.000MB/s transfers kernel: da0: 1907729MB (3907029164 512 byte sectors) kernel: da0: quirks=0x2<NO_6_BYTE>