[ale] how long will it take?

[Greg Freemyer]

On Thu, 04 Nov 2004 11:51:28 -0500, Geoffrey <esoteric at 3times25.net> wrote:
> Anyone have any idea how long it will take to do something like:
> 
> dd if=/dev/hda1 of=/dev/hda12
> 
> Where /dev/hda1 is 7 gig?
> 
> --
> Until later, Geoffrey
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> 
So, it has been five hours.  Has it finished yet?  I would not be
surprised if it had not.

You can do a quick raw speed test with dd if=/dev/hda1 of=/dev/null
bs=1M count=1000 and see how fast your raw hardware can read a GB
ignoring inefficientcies.

IIRC, a typical motherboard IDE controller can only do about 250MB/min
with a pure read (dd if=/dev/hda1 of=/dev/null), so your 7 GB would
take 28 minutes between IDE drives on different IDE channels.  (ie. No
inefficientcies).

OTOH, your command line is extremely inefficient because of all the
seeking you are doing.

Adding in the seeks between every few blocks and only using one
channel, I would think 50x slower, so maybe 25 hours!!!

As Sriad suggested, dd if=/dev/hda1 of=/dev/hda12 bs=100K would be
better, but I would go with bs=128MB or even bigger if you have the
RAM.

That should eliminate the seeking, so your only inefficientcy is the
single IDE channel.  Thus your speed should be about 1 hour (2 x
28min.).

Have you done any testing? Does any of the above sound right?

Greg
-- 
Greg Freemyer