[plug] dd speed estimates and /dev/hdx grepping

[Harry McNally]

On Thu, 23 Oct 2003 08:46:21 +0800 "Jay Turner" <jturner at bsis.com.au> wrote:

> So what are the ideal settings to use if one wishes to image one disk to
> another?
> 
> From the looks of it I would be wise to perform the following:
> 
> hdparm -d1 /dev/hdb
> hdparm -d1 /dev/hdc
> dd if=/dev/hdb of=/dev/hdc bs=?
> 
> This is where hda is my linux OS drive
> hdb is the source Win/Linux/Whatever drive (IDE0)
> hdc is the destination drive (IDE1)

If my ragged assumptions are true, I think a block size which is
half of the size of the cache in the drive you are writing to
would allow for some swing buffering. Otherwise use the cache
size. If you have the time, try both of these and see what difference
it makes.

If my assumptions overlook Linux mucking about with the block
lengths in transit to the disk then real performance diverges
uncertainly :-)

I'd be interested in your results and what data you uncover about
the drives themselves.
 
All the best
Harry

-- 
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