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Date: Fri, 31 Oct 2008 14:07:59 +0100 (CET)
From: Wojciech Puchar <wojtek@wojtek.tensor.gdynia.pl>
To: Jeremy Chadwick <koitsu@freebsd.org>
In-Reply-To: <20081031110159.GA30244@icarus.home.lan>
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	<20081031110159.GA30244@icarus.home.lan>
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Cc: Christoph Kukulies <kuku@kukulies.org>, freebsd-questions@freebsd.org
Subject: Re: fastest raw device copy?
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> In general, what you're doing is correct for a block copy.  There is
> nothing (that I know of) which is faster; you're copying 500GB of data
> (including the unused portion -- you *did* ask for a block copy),
> and this takes a long time.  Be patient.
>
> On the flip side, your blocksize (bs) there is quite high for no good
> reason.  I'd pick something more like bs=64k or bs=128k.  The default
> (512) is too small for what you want, but 10MBytes is silly.

should be big but less than drive's buffer, and be multiply of sector 
size.