[G4] HD size vs. performance

[jim carbone]

Hi,

I have a MDD Dual 1.25 2/ 2GB RAM running 10.4.7. I have a full boat  
of HDs in the case of various sizes. (2 160GB, a 120GB, and a 60GB-- 
all 7200rpm) as well as several firewire 400 and 800 HDs that I add  
and remove as needed depending on the task. Up until yesterday, I had  
my OS running on the original 60GB that came with the machine, but  
every now and then I get into the office in the morning to hear the  
machine doing a little "click-click-squeak click-click-squeak" dance.  
So, in fear of losing the drive, I shuffled things around and cloned  
it to the 160GB, which is now my startup.

I notice that it's a huge speed difference now. Apps like Word and  
Photoshop which used to open slowly, now pop open super-fast.  My  
question is: Is this a function of the fact that it was cloned to a  
new drive (almost like a major defrag) or is it because of the  
massive amount of free space on the drive? I feel like 160GB is gross  
overkill for the 28GB my OS drive uses (I have my iTunes and iPhoto  
libraries on other HDs).

Naturally, this is a question of curiosity. If it's running so much  
faster, I'm not rushing to change anything. But if I could get the  
same oh-so-fresh feeling from cloning it to one of the smaller HDs,  
the 160GB would be better used as backup/scratch disk space.

Any thoughts?

Thanks,
--jim