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Date:	Wed, 09 Jun 2021 18:19:43 -0700
From:	L A Walsh <cygwin AT tlinx DOT org>
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To:	"cygwin AT cygwin DOT com" <cygwin AT cygwin DOT com>
Subject:	odd prob for cygwin 'dd' from a character device on network disk
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I've been using a character device on linux in my
home directory named 'zero' that is a copy of the
'zero' device in /dev:
crwxrwxrw- 1 1, 5 Jun 15  2015 zero

to do read benchmarks using 'dd' (and write benchmarks
using a file named 'null' thats a copy of /dev/null).

I run it "occasionally", but not on a regular basis, since
it stays a bit boring.  Nevertheless, ballpark numbers
consistent with historical norms verify correct network
function (separate from read/write files).  Read/write speeds
at last check a few weeks ago were typical with
reads at 700MB/s and writes at about 300MB/s.

A few hours ago I tried it again due to some strange network
probs where I seemed to be getting file xfer speeds as low
as 200K/s.

I tried the bench script, and its half broken now -- because
I can no longer get anything back from the zero device
on my server via the network.  Locally, I can do 'dd' from
/dev/zero (or the zero file) and it takes a few seconds and
gave about 800MB/s.  So seemed to have been working fine,
but remotely -- still nada... reads 0 bytes from /dev/zero
and about 300MB/s write speed.

Can anyone think of anything that might have changed in
cygwin such that it would know the remote device is a
"/dev/zero".  Wondered if the 'dd' prog might have changed,
but just realize it did same with 'cat' as well.

Anyway -- I'm a bit stumped as to possible causes...
The writing to a remote /dev/null part is still working,
so not sure why one would change and not the other.

If anyone can think of anything, please let me know -- I'm
also gonna ping the samba list and maybe my distro list

Thanks!
-linda



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