Re: speed limitation with scp and sftp using openssh

I believe (but I haven't examined the protocol) that the issue is the ssh method
of multiplexing the connection. It is akin to trying to transfer via CIFS.

The protocol is more chatty that it needs to be for that one task when
done alone.
The thing is that the SSH protocol was designed to be able to have
multiple operations
happening at the same time. You can have four terminal sessions, four
file transfers
and multiple X windows forwarded at the same time, over the same SSH connection.

FTP just opens a TCP connection and sends the data raw, across it. Closing of
the connection signals end of the transfer. So FTP will always be the
fastest way
to send data across a TCP connection. (UDP is another matter)

Others that are familiar with the SSH protocol implementation would be able to
describe it in more detail, if you want.

On 2/23/06, Richard Labutis <unixrules1@xxxxxxxxx> wrote:
I am running aix 4.3, 5.1, 5.2, 5.3 using various
versions of openssh.

why is there a speed limit in copying files from one
machine to another. The speed appears to cap out at
around 7-8 mb/sec. This is on a gigabit network.
I know encryption has overhead, but not that much.
scp and sftp is the commands used to copy files.
It makes no difference what version of ssh/aix, it all
has the same results.

if I used rcp or ftp, it's very fast.


Any thoughts?


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