Using "dd" copy copy disk partitions
George Robbins
grr at cbmvax.commodore.com
Sun May 19 05:58:03 AEST 1991
In article <1991May18.170358.24367 at decuac.dec.com> mjr at hussar.dco.dec.com (Marcus J. Ranum) writes:
>
> Using dd to copy filesystems can also be a whole lot slower than
> using dump | restore, since dd will copy unused blocks as well as used
> ones, which dump is smart enough to avoid. In the filesystem is 1/2 full,
> dump | restore should be twice as fast as dd'ing the filesystem.
Wrongo! On any decent sized filesystemm, restore is *much* slower than
dump. You'd need a better than 2-1 ratio to make your point.
> I suppose there might be another benfit of using dump | restore
> since the filesystem will have a nice opportunity to lay stuff out in
> rotational proximity.
Optimist. 8-)
> One thing I can't remember - if you copy the 'c' device with
> dd, don't you also wind up replacing the bad block table on the destination
> disk with the bad block table from the donor? The possible side effects
> of that could be interesting.
Yes, but only with traditional devices that have the bad block information
within the C partition. These are becoing scarce.
--
George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr
but no way officially representing: domain: grr at cbmvax.commodore.com
Commodore, Engineering Department phone: 215-431-9349 (only by moonlite)
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