Re: Why SFTP performance sucks, and how to fix it

[Markus Friedl <markus%openbsd.org@localhost>]

On Tue, Jul 08, 2003 at 04:01:02PM +1200, Peter Gutmann wrote:
> In addition to the protocol-level handbrake, the SFTP protocol that runs on
> top of SSH contains its own handbrake.  This protocol recommends that reads
> and writes consist of no more than 32K of data, even though it's running over
> the reliable SSH transport which is in turn running over the reliable TCP/IP
> transport.  One common implementation limits SFTP packets to 4K bytes,
> resulting in a mere 4% link utilisation in the previously-presented scenario.

OpenSSH's SFTP client sends multiple read-requests before waiting
for a reply, so I don't think that the 32K limit is a big problem
(you can try to experiment with sftp(1)'s -B and -R option).