john at Corridors.wa.edu.au
Thu Jun 3 20:55:34 GMT 2004
Not being on the list, I didn't see this earlier.
> John wrote:
> > Possibly rsync can use ssh to forward a local port chosen the same way ftp
> > chooses a port fo active ftp. Then local rsync opens a connexion to
> > 127.0.0.1:port at the local end, and ssh forwards the stream to rsync running
> > as a daemon (on another randomly-chosen port? a user-specified port?) a the
> > destination.
> Bear in mind that this way you'll be encrypting the entire session
> instead of just the "Please start rsyncd for me" bit, so you'll likely
> suffer a speed hit depending on how powerful the two machines are.
In my case, I don't think I care. The sites are attached via the Internet so
bandwidth is the bottleneck.
> John also wrote...
> > I keep getting timeouts transferring between two ADSL accounts
> > and I've not decide whether to blame Arachnet (the ISP at both ends)
> > or rsync or even to suppose I'm expecting too much.
> As an aisde, I've had a problem similar to the one you describe with an
> unrelated service. Turns out the NAT table was dropping entries that
> went unused for 5 minutes, which meant the firewall started blocking
> return traffic as it appeared to be unrelated to any outgoing
> connection. I don't know if this would ever be an issue with rsync but
> it might be worth a look.
I've noticed the Billion does things like that and I think I have that cured.
Certainly my ssh sessions from home don't stall now, and I'm sometimes idle for
I've subseqently discovered two reasons my backups fail:
1. An ADSL connexion drops. It _should_ recover if the outage is very small, but I think on one occasion it stalled. Ultimately I decided nothing was happening and killed it.
2. rsync uses two much memory and the kernel lashes out at everything in sight.
Ultimately it lucks on the real offender and things go back to normal.
I don't know any way of estimating rsync's memory requirement (it may turn out
that rsync is unsatisfactory for our purpose), nor even any report of how much
As a workaround I've added half a gig (a nonsensical amount on this box) of
swap. So far I've not seen rsync use more than about half that.
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