Re: Slow USB3 drive (Intel amd64)

[Greg Troxel <gdt%lexort.com@localhost>]

Mark Carroll <mtbc%ixod.org@localhost> writes:

> I am trying out NetBSD 8.0 (GENERIC) on an Intel Broadwell NUC5i3RYK
> with USB3 ports on the front and back and finding them surprisingly slow
> with an external USB3 HDD. dmesg reports,
> usbdevs -d -v reports,
>
> addr 0: super speed, self powered, config 1, xHCI Root Hub(0x0000), vendor 8086(0x8086), rev 1.00(0x0100)
>   uhub0
>  port 1 addr 1: super speed, power 224 mA, config 1, Elements 25A2(0x25a2), Western Digital(0x1058), rev 10.19(0x1019), serial 57584D3141353733345A415A
>    umass0
>
> I don't see anything that makes me worry that I won't get USB3 speeds
> but,

Agreed; I think you are reading this correctly.

> # time dd if=/dev/sd0 of=/dev/null bs=1m count=1k
> 1024+0 records in
> 1024+0 records out
> 1073741824 bytes transferred in 393.518 secs (2728571 bytes/sec)
>       399.26 real         0.00 user         1.22 sys
>
> is rather slower than I had hoped (<3Mb/s reads?): at that speed it'll
> take a long time to cover the 2TB of the disk!

You are using the block device, not the raw device.   This traditionally
mattered on Unix and I think it might not on modern Linux.

Use /dev/rsd0d instead. I am hopeful that this is your only problem.

> I also tried a USB3 Seagate drive,
>  port 1 addr 5: super speed, power 224 mA, config 1, Expansion(0x231a), Seagate(0x0bc2), rev 7.06(0x0706), serial NA829NLT
> and got around the same data read rate.
>
> From the internal SSD it gets 58684036 bytes/sec so at least the problem
> seems limited to USB, ahcisata seems fine.

That seems slow.  I get (adding space ot make it readable)

  258 111 015 bytes/s rsd0d
   68 900 271 bytes/s sd0d

on a machine that's from 2010, with a decent but not exotic SSD.

Also, I recently tried out a USB3 samsung external SSD (again, not
exotic - just basic decent stuff).  I got around 100 MB/s, which is not
really fast, but way better than USB2.  But, I got mysterious read
errors about 100GB into the drive when reading back.  On USB2, it works
fine.  But, this is some maybe-sketchy USB3 add-on card that came with
my hand-me-down PC from a friend, that I have never used before.

>> xhci driver is at best experimental.

I'm not sure that's really true in 8.