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

["Howard Chu" <hyc%highlandsun.com@localhost>]

> -----Original Message-----
> From: ietf-ssh-owner%netbsd.org@localhost [mailto:ietf-ssh-owner%netbsd.org@localhost]On Behalf
Of Martin Pool

> On  8 Jul 2003, Peter Gutmann <pgut001%cs.auckland.ac.nz@localhost> wrote:
> > Another thing to keep in mind here is that if you signal a
> > read/write of the
> > entire file at once, the receiver knows how much disk space
> > it needs and can
> > lock the space before starting the receive
>
> I don't know of a means for a Unix or Windows server to "lock" disk
> space in that way.  I suppose the server might zero-fill the blocks
> between getting the start of the request and reading the bulk of it,
> but that seems highly contrived.

The FTP protocol has an ALLO command for allocating space in advance. On some
FTP servers I've seen, they do exactly this - zero-fill that much space. It
is a pretty foolproof way of accomplishing the task, even if it seems
contrived.

> > I'd really prefer to know before I start that a transfer is going to
> > fail, rather than write 2GB and then get the out-of-disk error.

Definitely.

  -- Howard Chu
  Chief Architect, Symas Corp.       Director, Highland Sun
  http://www.symas.com               http://highlandsun.com/hyc
  Symas: Premier OpenSource Development and Support