Speed problem

uwp at dicke-aersche.de uwp at dicke-aersche.de
Mon Nov 11 20:46:00 EST 2002

On Mon, 11 Nov 2002 tim.conway at philips.com wrote:

> I don't have a system with ssh available to check with (believe it or not,
> it's not approved for our network), but i think the sshd_config or

Unbelievable !

> ssh_config might be able to specify using compression as a default.  Is
> ssh on the sending side, perchance, using a lot of CPU?  I don't know of
> any cpu that can create anything close to a GB/sec compressed _input_,
> much less output.
> I don't even remember if you can turn the compression off if it IS
> default.

I can assure you, it's not compressed (I switch compression off because
the line is fast enough but the CPU gets slowed down with compression).
And I tried it with FTP. With FTP I'm getting 37 MB/s (almost the maximum
what the disks on the other side are able to write) and there's no loss of
speed whatsoever the whole time during the transmission.

> Barring that, If you aren't concerned about somebody sniffing the content
> you're syncing, perhaps you could use the internal transport?  If you can
> protect your ssh private keys, you can protect your rsync password-file as
> well.  This also has the advantage of cutting down on context switches, as
> one process is doing both the sync stream AND the communication.

This would be an option, but doing rsh with a root account is not
possible (couldn't get it to work, I haven't found any way to do it for root
and I really want to do it with the root account because I wanna have
the same file, directory and user permissions on the files) and also
not quite recommended... (.rhosts ??? Sheer horror ! ;-))
Maybe it is the encryption but I use ssh otherwise too and can get
on the same line results upto 12 MB/s (blowfish) and even 20 MB/s (arcfour)
without any loss of speed. The funny thing is, it seems to happen
only after a short while. The first 5 minutes seem to be going good,
almost 18 MB/s (also arcfour which means, this is very similar) and then
it goes down. It never goes up again, even when a new file get transferred,
but it starts at 18 MB/s when I start the complete rsync again.

BTW, if it wouldn't be for the deleting feature I could also use dmscp.
dmscp is a neat tool which uses ssh authentication but don't encrypt
the data so it's fast enough like FTP etc. Maybe there's a similar tool
outside with the deletion feature ?

Thanks !

      Udo Wolter <-> uwp at dicke-aersche.de        |  /"\
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