Hi,
On Thu, 09 Oct 2014 16:45:39 +0800
Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
> I got a different result with my machine. Below is the details.
> ...
> >>> Connected to USB 2.0 port via USB 1.1 hub:
> ...
> allen@allen-ivb:~$ sudo ddpt if=/dev/sg2 bs=512 bpt=240 count=65536
> verbose=2
> ...
> time to read data: 30.037081 secs at 1.12 MB/sec
>
> >>> Connected to USB 3.0 port via USB 1.1 hub:
> ...
> allen@allen-ivb:~$ sudo ddpt if=/dev/sg2 bs=512 bpt=240 count=65536
> verbose=2
> ...
> time to read data: 27.816240 secs at 1.21 MB/sec
That result is close to what I see with a "good" kernel (e.g. 2.6.33.20);
the USB3 port case was about 8% faster for you. It's only about 0.05%
faster on my system.
[For removable media, it's a good idea to disable polling for medium
changes before running a test. Depending on kernel & distribution that could
be achieved by doing
udisks --inhibit-all-polling
and/or for example
echo -1 >/sys/block/sdb/events_poll_msecs
before running the test.]
Mark
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