Re: Re: [nylug-talk] The Small Company's Guide to Hard Drive Failure and Linux

[Paul Wouters <paul () xtdnet nl>]

On Thu, 18 Nov 2004 alex () pilosoft com wrote:

> You need to do:
> dd if=/dev/hda of=/dev/hdc conv=sync,noerror bs=16384
>
> default blocksize of 512 is too small - doing read/write in 512 byte
> increments is very inefficient. increasing blocksize will however increase
> the size of "bad block", if there's a bad sector anywhere in 8192 byte
> block, you'll get zeros on the output. If there are no bad blocks, dd
> will be flyin' - much faster than any other method, assuming your disk is
> mostly full. If disk is <50% full, dd is slower than tar/untar.

There are some tools that do this for you. Read in large chunks, and when an
error happens lower the chunksize around it. I've used it to recover broken
flashmedia cards. One such tool is called 'ddresque' by I believe Kurt Garlof
(suse)

> > The other issue with dd is that typically replaces every sector on the
> > disk. So you'll need a disk EXACTLY the same size as the previous disk.

Just dd to a file and mount using -o loop

Paul
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