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Date:      Fri, 31 Oct 2008 14:16:38 +0100
From:      Ivan Voras <ivoras@freebsd.org>
To:        freebsd-questions@freebsd.org
Subject:   Re: fastest raw device copy?
Message-ID:  <gef0dq$l8a$1@ger.gmane.org>
In-Reply-To: <20081031110159.GA30244@icarus.home.lan>
References:  <490AC650.3000904@kukulies.org> <20081031110159.GA30244@icarus.home.lan>

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Jeremy Chadwick wrote:
> On Fri, Oct 31, 2008 at 09:48:16AM +0100, Christoph Kukulies wrote:

>> What would be the fastest way to do that sector by sector copy? I'm =20
>> using dd right now,
>>
>> dd if=3D/dev/ad0 of=3D/dev/da0 bs=3D10000000

> On the flip side, your blocksize (bs) there is quite high for no good
> reason.  I'd pick something more like bs=3D64k or bs=3D128k.  The defau=
lt
> (512) is too small for what you want, but 10MBytes is silly.

Not only that, but "10000000" isn't even correct - it needs to be a
multiple of sector size. Generally, using suffixes will do the right thin=
g:

dd if=3D/dev/ad0 of=3D/dev/da0 bs=3D1m


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