Toby Corkindale via luv-main
<[email protected]> writes:

> Hi,
> I've hit a strange issue with a new USB storage device.
> (Corsair Slider X2 64GB)
>
> On a Windows 10 laptop, it'll happily get ~75mbyte/sec writes.[1]
> Reads are even faster.
>
> However on my Linux workstation the best I can get is 27 mbyte/sec, and the
> usual speed more like 9-10 mbyte/sec. ie. Awful.
> Reads aren't much better, at 37mbyte/sec.
>
> The same workstation can happily read and write very fast to other USB 3
> storage devices, so I know the USB 3 ports are active.
>
> I've tested with vfat, ext4, btrfs and ntfs filesystems, plus just plain
> using "dd" to write to the raw device. In all cases, performance is
> terrible.
>
> I've played with mount options (sync, async, direct io, journal modes, etc)
> and it doesn't make a huge difference.
>
> I don't suppose anyone else has hit this, and might have a fix?
>
> (I'll test on an alternative Linux system tonight, with a slightly
> different Linux kernel and motherboard.)

Brainstorm things to check:

 * remove any unnecessary components e.g. USB hubs from the environment.

 * does dmesg complain about it?
 * does it draw too much power for that port?
 * are other port blocks (different chipset &c) OK?
   e.g. front panel is often worse.

 * Is it DEFINITELY doing more than USB2 theoretical max?
   Compare the speed you get to the max speed of USB2 and USB3.
   (IIRC USB2.0 is 480mbps = 60MiB/s).

 * is power saving being auto-enabled ever time you plug in the device,
   by some crack-smoking udev rule?  Remember to check the device *and*
   the internal hub.  If powertop --auto is involved, remove it while testing.

 * is the system doing a lot of fsyncs &c at the time?
   this can break even unrelated filesystems IME.

   The place I hit it was doing a dpkg install (many many syncs) while
   under heavy RRD write load (random access).

 * faint hope, but does SMART work with the drive?

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