I'm using rdiff-backup for backuping my data. Since some machines are using Windows I installed sshd and rdiff-backup with cygwin there. The backup works but is pretty slow. I then did some testing with scp, ssh copy over pipes, sftp and netcat between different systems. Between linux machines all is fine. Scp/ssh gives me about 70 MB/s. Over cygwin that speed drops down to about 8 MB/s. Using sftp or netcat gives good speeds though. I reach over 100 MB/s with netcat.
I tried using different ciphers and disabling compression. But that doesn't help. The machines are all recent ones with several gigs of ram and hardware raid. I tried it on different machines running cygwin and I get similar results. Should I use netcat and tunnel it? That seems like a lot configuration overhead. Rdiff-backup can't use sftp as it seems so I'm out of luck here. I don't want to use sshfs either since rdiff-backup uses a rolling checksum and I don't want to transfer all data for calculation.
Any idea what's causing that slowdown?
EDIT:
Information about cygwin environment:
Windows 2008 Storage Server Standard Ver 6.0 Build 6002 Service Pack 2
CYGWIN_NT-6.0 filer 2.0.4(0.287/5/3) 2015-06-09 12:22 x86_64 Cygwin
openssh 6.8p1-1
EDIT2
When I enable verbose output for scp between Linux and Windows I get:
debug2: channel 0: rcvd adjust 65536
The value is always the same for this transfer.
The same test between Linux and Linux gives me:
debug2: channel 0: rcvd adjust 114688
Here the value differs from time to time and values like 131072 or 147456 appear.
