<br><br><div class="gmail_quote">On Tue, Jul 13, 2010 at 5:56 PM, Mike Miller <span dir="ltr"><<a href="mailto:mbmiller%2Bl@gmail.com">mbmiller+l@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;">
<div class="im">On Tue, 13 Jul 2010, Robert Nesius wrote:<br>
><br>
> I think this is likely a case of bus-contention. Especially if the<br>
> reads and writes were being sent through the same bus/controller. I've<br>
> had similar issues when doing things with USB devices.<br>
<br>
</div>Maybe I would have better luck if I used a different pair of USB ports.<br>
I kinda doubt it because it seems like the big problem is with writes.<br>
Combining reading from one with writing to the other is definitely worse,<br>
but the major impact on system performance is coming from the writes.<br>
Maybe slowness of file transfers is an interaction of the two.<br>
<div class="im"><br></div></blockquote><div><br>I was thinking about this some more last night and I wasn't completely
happy with my hypothesis. I have actually noticed the "slowing down to a
crawl" behavior when copying from an internal hard-drive to a USB2
drive myself. A system reboot and repeat attempt sailed through with no
slowdown. I've always wondered about that - seems like our experiences
point to the microcontroller or driver. What is the brand of your
external drive? <br><br></div><blockquote class="gmail_quote" style="margin: 0pt 0pt 0pt 0.8ex; border-left: 1px solid rgb(204, 204, 204); padding-left: 1ex;"><div class="im">
</div>That sounds like part of the problem. Is there a better way to copy a<br>
collection of files and directories from one external USB HDD to another?<br>
I don't know how to do that with dd -- isn't that just for cloning?<br></blockquote><div><br>Assuming your block-sizes are the same you
can clone a smaller drive to a bigger drive with dd and use
partition-managing software to grow the partition. I've never done
that, but I'm pretty sure that's a way to do it. I'm also pretty sure
someone else on the list can confirm or deny that. :) <br><br>Lastly, when copying filesystems or very large directories, the key
thing to remember for speeding things up is that you're better off doing
intermediary transmissions as one huge bit-stream. So when I'm sending
things over a network I tar things up into a compressed tarball - send the tarball, then extract
the tarball on the other end - that can be faster than a straight rsync or network copy. I wouldn't think that necessary though with everything
connected to the machine. <br><br>-Rob<br><br></div></div>