Re: [SLUG] backup drive

From: Paul M Foster (paulf@quillandmouse.com)
Date: Tue Dec 09 2003 - 18:27:21 EST


On Mon, Dec 08, 2003 at 08:07:37PM -0500, Eben King wrote:

> Hi. I got a spare drive (hdc now), that is the same model (IBM/Hitachi
> IC35L120AVV207-0) as my main drive. Both are 120 decimal GB (~= 115
> binary GB). Right now I've set up a nightly 5am block copy copy (using
> dd) hda -> hdc. I realize this is not the most efficient method of copy,
> but as it's a personal system and unused at that time of the morning, the
> time taken isn't a problem. When I press the backup drive into service, it
> will appear as if the power had just been restored after an unclean
> shutdown. "sync" runs every minute to reduce the amount of data in
> unflushed buffers.
>
> The reason I wanted to do a block copy was that that was the only way I
> could think of to maintain partitions (if I repartition the main drive,
> the backup drive gets repartitioned automatically), and copy boot sectors
> and the like.
>
> Can anybody think of a better way to do what I'm trying to do?

Caution: dd will replicate errors on the source drive to the target
drive. But I don't know much else that makes byte-for-byte copies (of
course, that means almost nothing, since I never looked for an
alternative). And I suspect anything that makes an image copy will
replicate errors. In fact, this could be a problem if errors crop up on
your source drive, necessitating e2fsck. Those won't be fixed on your
target drive until your next image copy.

If you weren't trying to compensate for repartitioning and the like, I'd
say rsync is your best bet. I use it extensively, and it will keep
things completely in sync between the two drives.

Paul
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