Ian Smith <[email protected]> writes: > On Mon, 2 Jan 2017 12:59:49 +0300, Marat N.Afanasyev wrote: > > Ian Smith wrote: > > > > > > 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' > > > afair, single usb 2.0 device can be as fast as 240 Mbits/sec, not 320
280 Mbits/sec, actually. > > 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) 30816699 bytes/sec is a little over 30 Megabytes per second. Which is about right. Was someone misplacing a decimal? Or confusing bits with bytes? [Making things more confusing is that generally people refer to megabytes as 10e6 for disks and 2e20 for memory. For flash, it's the latter, but if you access it through a "disk" interface (like a thumb drive), you'll generally get 10e6 type numbers. > > > > it's the same drive in usb 2.0 port > > Ah, guess I've been taking "40.000MB/s transfers" for USB2 at its word. The 40MB/s number includes overhead, so you'll never get quite that high. > Testing 3 USB2 sticks in a USB2 port on my X200 (2.4GHz Core2Duo) I only > get about 18-20MB/s read for bs=1M count=1k, with little load although > 3k IRQ/s and 10k context switches/s, so I thought yours was good :) These things will vary with your hardware; both the driver chips in the computer and the flash stick itself. And some other things too, but I can't recall exactly. _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
