Comment by rapier1
2 days ago
Keep in mind that SCP/SSH might be faster in some cases than SFTP but in both cases it is still limited to a 2MB application layer receive window which is drastically undersized in a lot of situations. It doesn't matter what the TCP window is set to because the OpenSSH window overrides that value. Basically, if your bandwidth delay product is more than 2MB (e.g. 1gbps @ 17ms RTT) you're going to be application limited by OpenSSH. HPN-SSH gets most of the performance benefit by normalizing the application layer receive window to the TCP receive window (up to 128MB). In some cases you'll see 100X throughput improvement on well tuned hosts on a high delay path.
If your BDP is less than 2MB you still might get some benefit if you are CPU limited and use the parallel ciphers. However, the fastest cipher is AES-GCM and we haven't parallelized that as of yet (that's next on the list).
When I need speed, I drop down to FTP/rcp or some other cleartext protocol.
Moving a terabyte database in an upgrade, I have connected three ports direct (no switch), then used xargs to keep all three connections busy with transferring the 2gb data files. I can get the transfer done in under an hour this way.
I don't currently have a performance need for an encrypted transfer, but one may arise.
I fully understand that. We're using this, along with parsyncfp2 (which you should checkout) to move 1.5PB of data a month across a 40Gb link. Not saying that HPN-SSH is only useful in that context but different people certainly do have different needs.