Date: Fri, 9 Jul 2010 08:31:52 -0500 From: David Kelly <dkelly@hiwaay.net> To: Robert Bonomi <bonomi@mail.r-bonomi.com> Cc: freebsd-questions@freebsd.org Subject: Re: slow down dd - how? Message-ID: <20100709133152.GA40320@Grumpy.DynDNS.org> In-Reply-To: <201007090644.o696i0QK028217@mail.r-bonomi.com> References: <201007090644.o696i0QK028217@mail.r-bonomi.com>
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On Fri, Jul 09, 2010 at 01:44:00AM -0500, Robert Bonomi wrote: > > > > > How can I slow down dd? > > > > you could use some creative shellscripting (probably in addition to idprio): > > > > dd if=/dev/zero bs=1024k | ( dd bs=1024k count=10; sleep 3 ) | dd bs=1024k of=/dev/somewhere > > > > This pauses for 3 seconds for every 10MB written. ... > > I must be missing something. You are not missing anything. > Doesn't that "dd ... ; sleep" in the sub-shell need to be in a _loop_ > of some sort? Yes. dd if=/dev/zero bs=1024k | ( dd bs=1024k count=10; sleep 3 ) | dd bs=1024k of=/dev/null 0+10 records in 0+10 records out 655360 bytes transferred in 0.001183 secs (554077619 bytes/sec) 0+10 records in 0+10 records out 655360 bytes transferred in 3.003105 secs (218227 bytes/sec) > I would expect the dd in the sub-shell to _exit_ after the first 10mb, > whereupon the subshell would exit after the 3 second sleep, whereupon > 'somebody" is going to holler about a 'broken pipe'. Am not sure why the actual example blocksize was 64k but the results are the same for FreeBSD and MacOS X. -- David Kelly N4HHE, dkelly@HiWAAY.net ======================================================================== Whom computers would destroy, they must first drive mad.
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