Replacing a failing HD

Gayn Winters gayn.winters at
Wed Oct 19 19:42:25 PDT 2005

> -----Original Message-----
> From: owner-freebsd-questions at 
> [mailto:owner-freebsd-questions at] On Behalf Of 
> Ramakrishna Nalla
> Sent: Tuesday, October 18, 2005 9:52 PM
> To: Bob Ababurko
> Cc: freebsd-questions at; Craig Deal
> Subject: Re: Replacing a failing HD
> But, won't doing a dd between two disks with incompatible 
> sizes create a bad partition table on the destination drive?
> TIA,
> Rama

Not really a "bad" partition table, if what you mean is bad=corrupted.
Using dd you copy blocks, and this will correctly bring the partition
table along.  What you do not get initially is the full utilization of
the larger drive.  Thus if you dd a 40GB drive (or slice) to a 60GB one,
you'll only get the image of the 40GB drive that is initially usable.
You will have 20GB that is not - at least initially - usable.  Nothing
stops you from reorganizing the larger disk, however.

I think the original problem in this thread was a quick save of a
failing disk.  dd is great for this.  If you were simply going to
utilize a larger disk, then you'd be better off using fdisk to slice it
up, creating your bsd partitions and then using dump|restore to get
things where you want them.  I think the Handbook has a nice section on
doing this.


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