How can I speed up a dd copy?

Nathan Kinkade nkinkade at
Fri Jan 14 07:13:35 PST 2005

On Thu, Jan 13, 2005 at 04:38:14PM -0800, Drumslayer2 wrote:
>  Hello
>  When I am performing a dd between (2) 36 Gig 160
> disks (to duplicate them) it takes about 2.5 hrs. Is
> there any way I can speed this up? Is there any better
> way I can clone a bootable main disk?
>   Thanks
>   NH.

Using dump(8) and restore(8) works well for me and it eliminates the
need that the disks should be the same size.  It may seem like a lot of
work at first, but once you have done it a few times it can be done very
fast.  The benefit being that you don't waste massive amounts of time
copying null blocks from disk to disk.  A few months ago I wrote up a
quick howto for the guys where I work.  I make no guarantee that the
directions are perfect for everyone, but they work fine here.  It also
assumes you are booting to a good installation of 5.x whose version of
dump supports the dumping of "live" filesystems (I don't think the
version with 4.x supported this, or at least not 4.8 - someone correct
me if I'm wrong).  However, you could just as easily boot to one of the
FreeBSD install disks and eliminiate the need for a "live" dump in the
first place.

For reference, you can take a look at the short instructions I wrote up

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