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Date:	Fri, 10 Nov 2006 14:20:00 -0800
From:	Linda Walsh <cygwin AT tlinx DOT org>
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To:	cygwin AT cygwin DOT com
Subject:	Re: cyg mem limit or network failure? Other? dd(dsk->net).blksz>=64M: Fail
References:	<4552ED55 DOT 7030007 AT tlinx DOT org> <20061109110013 DOT GD18141 AT calimero DOT vinschen DOT de>
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Corinna Vinschen wrote:
> On Nov  9 00:56, Linda Walsh wrote:
>   
>> I was running some network bandwidth tests using "dd" (WinXP2/Cygwin)
>>
>> I was timing copies of a 300MB file from local disk to a remote
>> server.  The local computer has enough memory to hold the file
>> in the memory cache once it is loaded.
>>
>> I ran through increasing power-of-two block sizes from
>> 512 bytes up to 512MB, where it, theoretically could read
>> and write the file in one read and write for the whole file.
>> Essentially (say "s:" is a network drive):
>>
>> for (i = 512;  i<=512MB;  i = i*2) do {
>>    dd  bs=$i  if=/tmp/input  of=/s/Video/output.dat
>> }
>> Unfortunately, the test /fails/ at or above 64MB with:
>>     dd: writing '/s/Video/output.dat': Resource temporarily unavailable
>>     
> I tried this with a 120 Megs and 1.2 Gigs file and dd works with all
> blocksize up to the tested 512 Megs for me.
>
> Could this be a network issue with big blocksizes, maybe
---
    Perhaps...though just tried it again with 32M, 64M, 128M 256M 512M and
using /dev/zero as input.  That works up through 256M.  Will have to try
looking at this some more later...strange.  Thanks for the feedback.

linda


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