A long while ago I posted my first version of the comparison of libssh vs libssh2. I have since then kept it updated and modified it over time. (Reminder: I am the libssh2 maintainer)

In that page, I included the performance differences I had measured which at the time showed libssh2 to be significantly faster when doing SCP operations.

The libssh guys always claimed I was wrong:

Please don’t be ridiculous. No competent network developer will take you seriously when you tell that libssh2 is 2.3 times faster that libssh.

and have even used rather harsh words when saying so.

you read this FUD page on the libssh2 website. I don’t want to start arguing here, the page is complete crap

(These two quotes are from the two leading libssh developers.)

Due to their complaints I withdrew the mentioning of the speed differences from the comparison page. Maybe I had done something wrong after all and since I didn’t care properly to go back and verify my methods and redo everything, I decided to just take it off until I have more backing or more accurate tests.

Fast forward to current time and Mark Riordan does his extensive performance tests of various SSH/SFTP implementations. He mailed the libssh mailing list about it, and his test results are interesting. I’m including it below for easier reading and just in case Mark’s original won’t be around as long as this.

It repeats very similar numbers to mine and shows the same speed difference that I was told cannot happen. Isn’t that funny? Am I still ridiculous?

SSH file transfer performance

The following table summarizes performance of SSH clients.

					LAN: 1 Gbit/sec		WAN: 6 Mb down, 0.9 Mb up
Solaris x86 server
Client	Client OS	Server	Comp Enable	File Cmp	UL MB/s	DL MB/s	UL MB/s	DL MB/s
libssh2	Win	Solaris	No	No	0.147	12.2
libssh2	Win	Solaris	Yes	No
libssh2	Linux	Solaris	No	No	0.82	11.8
libssh2	Linux	Solaris	Yes	No
libssh 0.4.6	Win	Solaris	No	No
Bitvise Tunnelier	Win	Solaris	No	No	13.50	3.95
Bitvise Tunnelier	Win	Solaris	Yes	No	8.541	10.2
psftp	Win	Solaris	No	No	9.4	5.06 or 0.46
WS_FTP 12.3	Win	Solaris	No	No	8.07	7.65
Ubuntu sftp	Linux	Solaris	?	No	29.6	11.5
Linux server
libssh2	Win	Linux	No	No	9.5	8.1	0.059	0.26
libssh2	Win	Linux	Yes	No
libssh2	Linux	Linux	No	No	7.4	7.4	0.083	0.267
libssh 0.4.6	Win	Linux	No	No	15.4	2.8	0.10	0.13
libssh 0.4.6	Linux	Linux	No	No	8.97	2.8	0.099	0.189
libssh 0.4.6	Linux	Linux	Yes	Yes	19.7	3.3
libssh latest	Win	Linux	No	No	14.1	1.38
psftp	Win	Linux	No	No	4.59	6.58	0.070	0.10
WS_FTP 12.3	Win	Linux	No	No	23.0	8.5	0.113	0.361
Bitvise Tunnelier	Win	Linux	No	No
Ubuntu sftp	Linux	Linux	No	No	16.2	6.6	0.11	0.51

What about SFTP?

It should be noted that in my original claim and in this test above we speak SSH speeds (like SCP), not SFTP. SFTP has its own slew of problems and libssh2 is in fact not very good at doing SFTP speedily yet. We have work in progress to improve this situation, but we’re not there yet. I’ll post a follow-up on SFTP speeds soonish as things have been developing nicely in there recently.

What about speeds compared to other clients?

libssh2 is not fully on par with for example openssh when it comes to raw SCP speed, but it is in the same “neighborhood”.