Replacing a failing HD

Jerry McAllister jerrymc at clunix.cl.msu.edu
Wed Oct 19 07:04:16 PDT 2005


> 
> But, won't doing a dd between two disks with incompatible sizes create a bad
> partition table on the destination drive?

Basically yes, at least an incorrect one, even if you can make it work.

It is much better to build your slices, partitions and file systems
and then move your old data using dump(8)/restore(8) than to try
and dup a drive with dd.   Even if they are nominally the same size,
they may have some difference.

////jerry

> TIA,
> Rama
> 
> On 10/19/05, Bob Ababurko <ababurko at adelphia.net> wrote:
> >
> > Craig Deal wrote:
> > >
> > >
> > >>>Hope it's ok to continue this thread, but can you explain in more
> > >>>detail how to use dd to copy a HD. I read "man dd" and was
> > >>
> > >>unable to
> > >>
> > >>>figure out how this is done.
> > >>>
> > >>>Thanks,
> > >>>Craig
> > >>>
> > >>>_______________________________________________
> > >>>freebsd-questions at freebsd.org mailing list
> > >>>http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> > >>>To unsubscribe, send any mail to
> > >>
> > >>"freebsd-questions-unsubscribe at freebsd.org"
> > >>
> > >>This is what I have done in the past.
> > >>
> > >>dd if=/dev/da0 of=/dev/da1 bs=8192b
> > >>
> > >>where da0 is the disk you want to copy and da1 is the new,
> > >>blank disk.
> > >>I should also mention that it is wise to do this in single
> > >>user mode. I actually have read this somewhere and
> > >>understand the point of it, but I must also say that I have
> > >>done it both ways and they have both worked.
> > >>YMMV I would have to say it is all dependant and what you
> > >>have running.
> > >>
> > >>I have done this too many times to count and it is very easy.
> > >>
> > >>peace,
> > >>Bob
> > >>_______________________________________________
> > >>freebsd-questions at freebsd.org mailing list
> > >>http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> > >>To unsubscribe, send any mail to
> > >>"freebsd-questions-unsubscribe at freebsd.org"
> > >>
> > >
> > >
> > > I tried this and got the following error:
> > >
> > > ad0: FAILURE - READ_DMA status=51<READY,DSC,ERROR>
> > error=40<UNCORRECTABLE>
> > > LBA=8387712
> > >
> > > Any ideas what the problem might be? Do the hard drives have to be
> > > identical? One is a 30Gb and the other is a 60GB.
> > >
> > > Thanks,
> > > Craig
> > >
> > > _______________________________________________
> > > freebsd-questions at freebsd.org mailing list
> > > http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> > > To unsubscribe, send any mail to "
> > freebsd-questions-unsubscribe at freebsd.org"
> > >
> >
> > I would think that you can dd from a small drive to a large drive, but
> > if the is possible _definitely_ not the other way around. Which size
> > are source and dest. drive?
> >
> > -Bob
> > _______________________________________________
> > freebsd-questions at freebsd.org mailing list
> > http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> > To unsubscribe, send any mail to "
> > freebsd-questions-unsubscribe at freebsd.org"
> >
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> 



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