Date: Mon, 02 Jan 2017 12:09:11 -0500 From: Lowell Gilbert <freebsd-stable-local@be-well.ilk.org> To: Ian Smith <smithi@nimnet.asn.au> Cc: "Marat N.Afanasyev" <amarat@li.ru>, FreeBSD stable <freebsd-stable@freebsd.org> Subject: Re: usb 3.0 thumb drive speed limit Message-ID: <44shp1l77s.fsf@lowell-desk.lan> In-Reply-To: <20170102212552.O26979@sola.nimnet.asn.au> (Ian Smith's message of "Mon, 2 Jan 2017 22:14:01 %2B1100 (EST)") References: <586A0F05.6050504@li.ru> <20170102202711.G26979@sola.nimnet.asn.au> <586A2495.5030301@li.ru> <20170102212552.O26979@sola.nimnet.asn.au>
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Ian Smith <smithi@nimnet.asn.au> 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.
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