lazarus speed

Hi !

First, I really want to thank the authors of The Coroner Toolkit, it seems 
that I'll be ablse to get some of my wiped data back :)
But, I have a question, my erased file system was 30Go big.
I already finished the unrm part and started the lazarus part. But it seems to 
take forever.
After 3 hours, I only have like 150Mo in the blocks directory. Now, I'm using 
a USB hard drive (this is all I have at the time that has enough space on 
it). So, if I changed it to a regular internal HDD, would it be faster, or 
the slowness doesn't come from the drive but from tct itself ?

Thanks in advance for your answers.

Antoine