Never ending cloning with dd on SystemRescueCD for PowerPC

[SOSdonnees]

Hi,

Can someone explain why does this Linux command results in a never ending drive cloning ?

Code:

dd if=/dev/hda of=/dev/sdb bs=1024 count=100000000 conv=noerror

where hda is 60 GB and sdb is 320 GB.

Maybe is the count parameter needless, but my assuption was it would copy 100 Mio blocks, each 1024 bytes, i.e. about 100 GB.
I hoped the command being interrupted when reaching the end of the 60 GB input drive.

The command is run from SystemRescueCD-PPC 0.2.0 on an iBook G4 2005.
Well, the cloning is slow as on USB and the notebook has few RAM, but it's running for about 20 hours though ...

[SOSdonnees]

Update :

When stopping the dd command, the following output is printed :

Code:

21182957+0 records in
21182956+0 records out

So, only about 21 GB were copied in as many hours.

How can the cloning speed be so slow (1 GB/hour) (assuming that the drive is healthy) ?

The iBook is from 2005, ans has USB 2.0.

RAM is 512 MB, on the motherboard.
This is the only explanation that I could find to so slow cloning speeds.
My assumption is that SystemRescueCD occupies a large place of the existing RAM, leaving little RAM for running processes.
According to the specifications, I could extend the RAM to 1,5 GB as the two RAM sockets are empty.
Maybe should I add more RAM and then go on using the skip & seek parameters.

As ddrescue is not available on this version of SystemRescueCD, I don't know if some bad sectors were found.
However, the drive looks healthy as the iBook starts Mac OS without issue.

N.B. Extracting the drive from this iBook is complicated (~30 steps on iFixit), hence the cloning using a live CD and the USB port.