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From: mjr@hussar.dco.dec.com (Marcus J. Ranum)
Newsgroups: comp.unix.ultrix
Subject: Re: Using "dd" copy copy disk partitions
Message-ID: <1991May18.170358.24367@decuac.dec.com>
Date: 18 May 91 17:03:58 GMT
References: <8410@jhunix.HCF.JHU.EDU> <3168@shodha.enet.dec.com>
Organization: Digital Equipment Corp., Washington Ultrix Resource Center
Lines: 16


	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.

	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.

	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.

mjr.