On Tue, Sep 25, 2012 at 10:33 PM, Emmett Culley <emmett at webengineer.com> wrote: > I have been using BackupPC via rsync daemons on the target machines and all has been working well. At least until about the time rsync went to version 3.0.6. > > Since then backups have been failing for some targets. The failure is a TCP ZeroWindow issue. It looks like the server rsync process cannot empty it's buffer soon enough and eventually the process fails. > > I really do not know if it is rsync version related, because I never looked at the packet stream until I started having failures. > > BackupPC was running on a VM host and the failing machine was one of the guest VMs. I tried upgrading rsync to 3.0.9 and that didn't help. > > So I moved the BackupPC set up to a different server (no VM). Not all backups are working. though I still see some ZeroWindow packets along with a few retransmision packets. But the backup completes on all machines, including the VM that was failing before. > > I've googled rsync zerowindow and found some references, but none seemed to apply to my situation. > > Anybody else having a similar experience? I found an old mention of turning off TCP window scaling solving a problem with rsync (not involving backuppc). Seems unlikely but might be worth a try: sysctl -w net.ipv4.tcp_window_scaling=0. -- Les Mikesell lesmikesell at gmail.com