[Cialug] Why is rsync/SSH so much faster than rsync/nfs?

[Ken MacLeod]

On Sun, Aug 8, 2010 at 11:55 AM, Matthew Steven <matthew at geniusweb.com> wrote:
> When I switch to using rsync over ssh to copy, the transfer speeds,
> particularly with lots of smaller files, goes way up. I don't know if
> it's because rsync is filling the packets more efficiently when
> operating over ssh, or if nfs is badly configured?
>
> Seems to me that nfs should have a bit less overhead than ssh.

Over NFS, rsync will do several system calls to stat(2) and open(2)
each file that will result in round-trip requests to the server to get
replies.  Over SSH, those system calls are done locally on each end
and only the file data is transferred over the network.

This symptom of NFS is pretty specific to scanning across a large part
of a filesystem (rsync, find).  It doesn't really affect diskless
clients and I wouldn't worry about trying to tune NFS for it.

  -- Ken