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Date: Thu, 30 Sep 2004 09:53:22 -0500 (Central Daylight Time)
From: "David A. Rogers" <darogers AT speakeasy DOT net>
To: cygwin AT cygwin DOT com
Subject: RE: cp to flash drive very slow
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Thanks for responding, Gary.

> Regardless, <3.7Mb/second seems like something's wrong somewhere.  Are you
> running USB2.0 hub-to-device?

I dunno.  I'm not very knowledgable about hardware esp. USB.  How would I
tell?

dar

On Wed, 29 Sep 2004, Gary R. Van Sickle wrote:

> > I tried using cp to copy a zip file 106MB from my hard drive
> > to my flash drive (sandisk mini cruzer).  After 20 minutes it
> > still had not completed.
> >
> > xcopy copied the file in 22 seconds.
> >
> > Why would cp be so much slower?  Any ideas as to work-arounds?
> >
>
> Last I checked, cp was slower on network copies than xcopy was, but the
> difference was nowhere *near* that dramatic.  I can offer a few guesses
> here:
>
> 1.  Again last I looked, cp was using fopen()/fread() et al to do the copy.
> Good for portability, bad for efficiency.  Xcopy is probably using
> CopyFile{Ex} or some such lower-level funcion, which if MS is on the ball
> (yeah I know) involves a lot fewer layers of code, and if we're really good
> maybe is even copying raw sectors using scatter/gather (yeah I know I'm
> dreaming, but maybe).
>
> 2.  Caching.  Xcopy may be caching your writes to flash, cp may be forcing a
> flush somehow.  I've had similar copies take essentially no time, only to
> find out that the copy never actually got committed to disk until much much
> later.  XP SP1 doesn't default to that behavior IIRC, but check to make sure
> that you do NOT have that option turned on, or you WILL lose data.
>
> Regardless, <3.7Mb/second seems like something's wrong somewhere.  Are you
> running USB2.0 hub-to-device?
>
>


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