Very slow operation across the Internet

[Björn Persson]

I'm trying to use Obnam to back up one computer to another over SFTP.
The data to be backed up includes a large number of small files, most
of which don't change from one backup run to the next. This works
reasonably well on a local network where there is nothing but two
cables and a switch between the two computers. There a backup run takes
about an hour and a half when there are earlier generations on the
server and the changes are relatively small.

Across the Internet it's a different story. A backup run that started
early Wednesday morning was still running when I had to unplug the
laptop on Friday afternoon. The log shows no long outages but slow and
steady operation at a rate of a few directories per minute.

Bandwidth is not the bottleneck, so I have to assume that the increased
latency makes the difference – that a very large number of synchronous
requests with a latency of about a tenth of a second add up to several
days of runtime.

My question to the list is: Do others see this too, or does the extreme
slowness indicate that I have configured something terribly wrong?

Björn Persson