Re: rsync to copy files?

[Bob Friesenhahn]

On Wed, 23 Jun 2004, Warren Young wrote:

> Bob Friesenhahn wrote:
> > I have learned that using 'rsync' to copy files improves the install time 
> > quite dramatically for repeat installs. 
>
> This should only be true when the transfer channel is much slower than the 
> disks on which the files are stored.  rsync must read both the source and 
> destination files, and do calculations on both, before it knows which parts 
> of the files need to be transferred.  When the transfer channel is a network, 
> it's likely that the time spent doing this extra disk I/O and calculation is 
> more than offset by the savings in network time.  When the source and 
> destination are on the same machine, there should be no such benefit.

That is true.  However, usually reading is faster than writing, 
particularly if NFS is involved.  Also, rsync can first check both the 
file's timestamp and size.

In my test case, the source files are accessed via NFS (over 
100BASE-T), and the 'make install' is executed on the target system.

> Instead of chasing this solution, try patching autoconf to use 'cp -u' 
> instead of 'install'.

I was not aware of this cp option. It seems to be limited to GNU 
cp.  On Linux systems, or systems where GNU cp is available, this 
seems like a reasonable choice.

Bob
======================================
Bob Friesenhahn
address@hidden
http://www.simplesystems.org/users/bfriesen