On 09/25/2012 08:33 PM, Emmett Culley wrote: > 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. If the rsync server sends a TCP ZeroWindow packet to a client, that probably indicates that the server is either hung or looped. Either way, it has stopped reading data from the socket, and the kernel sends ZeroWindow to the client's host to indicate that the client should stop sending data. You may have found a bug in rsync that the developers need to resolve. Have you tried attaching strace to the rsync server process when it hangs?