Rsync resource consumption, whilst building a large file list

[Forrest Aldrich]

I need to rsync a large collection of files (images) that number in the 
1000's.  We have 2 repositories, one was mass-copied recently, the other 
has since had updates performed.   The initial copy took over 5 hours to 
complete ;-)  What we want is only to update the destination (old) copy 
with newer files, delete anything that shouldn't be there.

What I'm trying to determine is how rsync uses resources whilst building 
the comparison lists.

Does rsync build a file tree to a temp file, or is it doing this in memory?

I checked through the manpage, and didn't see anything that mentioned 
this - or did I overlook something.


Thanks.