5 ms·
High Performance SSH/SCP
- josephg 10mo agoAny chance this work can be upstreamed into mainline SSH? I'd love to have better performance for SSH, but I'm probably not going to install and remember to use this just for the few times it would be relevant.
- harvie 10mo agoAlso upstream is extremely well audited. That's a huge benefit i don't want to loose by using fork.
- Bad_CRC 10mo agothis, I'm not going to start using a random ssh fork with modified ciphers.
- Zambyte 10mo agoIt may still be sensible if you only expose it to private networks.
- bomewish 10mo agoSo could this safely be used on Tailscale then ? I’m very curious though also a bit paranoid.
- gear54rus 10mo agoIt could safely be used on public internet, all this fearmongering has no basis under it. Better question is 'does it have any actual improvements in day-to-day operations'? Because it seems like it mostly changes up some ciphering which is already very fast.
- Zambyte 10mo agoI'm not fear mongering. I'm just saying - IF you don't trust it - AND you want to use it => run it on a private network You don't have to trust it for security to use it. Putting services on secure networks when the public doesn't need access is standard practice.
- joecool1029 10mo agoI remember the last time I really cared to look into this was in the 2000’s, I had these wdtv embedded boxes that had a super anemic cpu that doing local copies with scp was slow as hell from the cipher overhead. I believe at the time it was possible to disable ciphers in scp but it was still slower than smbfs. NFS was to be avoided as wifi was shit then and losing connection meant risking system locking up. This of course was local LAN so I did not really care about encryption. But I don’t miss having those limitations.
- rapier1 10mo agoIt's still possible but we only suggest doing it on private known secure networks or when it's data you don't care about. Authentication is still fully encrypted - we just rekey post authentication with a null cipher.
- yjftsjthsd-h 10mo ago> It could safely be used on public internet, all this fearmongering has no basis under it. On what basis are making that claim? Because AFAICT, concern about it being less secure is entirely reasonable and is one of the big caveats to it.
- rapier1 10mo agoConcern about it being less secure is fully justified. I'm the lead developer and have been for the past 20 years. I'm happy to answer any questions you might happen to have.
- messe 10mo ago> So could this safely be used on Tailscale then ? I’m very curious though also a bit paranoid. You may as well just use tailscale ssh in that case. It already disables ssh encryption because your connection is encrypted with WireGuard anyway.
- emilfihlman 10mo agolose*
- rapier1 10mo agoI do want to say that HPN-SSH is also well audited; you can see the results of CI tests on the github. We also do fuzz testing, static analysis, extensive code reviews, and functionality testing. We build directly on top of OpenSSH and work with them when we can. We don't touch the authentication code and the parallel ciphers are built directly on top of OpenSSL. I've been developing it for 20+ years and if you have any specific questions I'd be happy to answer them.
- Almondsetat 10mo agoOpenSSH is from the people at OpenBSD, which means performance improvements have to be carefully vetted against bugs, and, judging by the fact that they're still on fastfs and the lack of TRIM in 2025, that will not happen.
- wahern 10mo agoThere's nothing inherently slow about UFS2; the theoretical performance profile should be nearly identical to Ext4. For basic filesystem operations UFS2 and Ext4 will often be faster than more modern filesystems. OpenBSD's filesystem operations are slow not because of UFS2, but because they simply haven't been optimized up-and-down the stack the way Ext4 has been Linux or UFS2 on FreeBSD. And of course, OpenBSD's implementation doesn't have a journal (both UFS and Ext had journaling bolted late in life) so filesystem checks (triggered on an unclean shutdown or after N boots) can take a long time, which often cause people to think their system has frozen or didn't come up. That user interface problem notwithstanding, UFS2 is extremely robust. OpenBSD is very conservative about optimizations, especially when they increase code complexity, and particularly for subsystems where the project doesn't have time available to give it the necessary attention.
- chasil 10mo agoOpenBSD UFS did have "soft updates" which were some kind of alternative to journaling. I believe that these were recently removed. Perhaps they don't play well with SMP.
- throw0101d 10mo agoMcKusick, who wrote the original BSD FFS, also later came up with SU: * https://en.wikipedia.org/wiki/Soft_updates https://en.wikipedia.org/wiki/Soft_updates
- suprjami 10mo agoUnlikely. These patches have been carried out-of-tree for over a decade precisely because upstream OpenSSH won't accept them.
- rapier1 10mo agoMore than 2 decades at this point. The primary reasons is that the full patch set would be a burden for them to integrate and they don't prioritize performance for bulk data transfers. Which is perfectly understandable from their perspective. HPN-SSH builds on the expertise of OpenSSH and we follow their work closely - when they make a new release we incorporate it and follow with our own release inside of a week or two (depending on how long the code review and functionality/regression testing takes). We focus on throughput performance which involves receive buffer normalization, private key cipher speed, code optimization, and so forth. We tend to stay clear of anything involve authentication and we never roll our own when it comes to the ciphers.
- hsbauauvhabzb 10mo agoDepending on your hardware architecture and security needs, fiddling with ciphers in mainline might improve speed.
- Bender 10mo agoI doubt this would ever be accepted upstream. That said if one wants speed play around with lftp [1]. It has a mirror subsystem that can replicate much of rsync functionality in a chroot sftp-only destination and can use multiple TCP/SFTP streams in a batch upload and per-file meaning one can saturate just about any upstream. I have used this for transferring massive postgres backups and then because I am paranoid when using applications that automatically multipart transfer files I include a checksum file for the source and then verify the destination files. The only downside I have found using lftp is that given there is no corresponding daemon for rsync on the destination then directory enumeration can be slow if there are a lot of nested sub-directories. Oh and the syntax is a little odd for me anyway. I always have to look at my existing scripts when setting up new automation. Demo to play with, download only. Try different values. This will be faster on your servers, especially anything within the data-center. ssh mirror@mirror.newsdump.org # do this once to accept key as ssh-keyscan will choke on my big banner mkdir -p /dev/shm/test && cd /dev/shm/test lftp -u mirror, -e "mirror --parallel=4 --use-pget=8 --no-perms --verbose /pub/big_file_test/ /dev/shm/test;bye" sftp://mirror.newsdump.org For automation add --loop to repeat job until nothing has changed. [1] - https://linux.die.net/man/1/lftp https://linux.die.net/man/1/lftp
- zenoprax 10mo agoWow, I hadn't heard of this before. You're saying it can "chunk" large files when operating against a remote sftp-subsystem (OpenSSH)? I often find myself needing to move a single large file rather than many smaller ones but TCP overhead and latency will always keep speeds down.
- aidenn0 10mo agoI use lftp a lot because of it's better UI compared to sftp. However, for large files, even with scp I can pin GigE with an old Xeon-D system acting as a server.
- zenoprax 10mo agoYes, for local access this is my experience too. For trans-oceanic file transfers I can really see the limits and parallelization is essential.
- frantathefranta 10mo agoI admittedly don't really know how SSH is built but it looks to me like the patch that "makes" it HPN-SSH is already present upstream[1], it's just not applied by default? Nixpkgs seems to allow you to build the pkg with the patch [2]. [1] https://github.com/freebsd/freebsd-ports/blob/main/security/openssh-portable/files/extra-patch-hpn https://github.com/freebsd/freebsd-ports/blob/main/security/... [2] https://github.com/NixOS/nixpkgs/blob/d85ef06512a3afbd6f90825dd8f5b6cef017bdd6/pkgs/tools/networking/openssh/default.nix#L40 https://github.com/NixOS/nixpkgs/blob/d85ef06512a3afbd6f9082...
- yjftsjthsd-h 10mo agoUpstream is either OpenBSD itself or https://github.com/openssh/openssh-portable https://github.com/openssh/openssh-portable , not the FreeBSD port. I'm... not sure why nix is pulling the patch from FreeBSD, that's odd.
- gorgoiler 10mo agoThere’s a third party ZFS utility (zrepl, I think) that solves this in a nice way: ssh is used as a control channel to coordinate a new TLS connection over which the actual data is sent. It is considerably faster, apparently.
- rapier1 10mo agoI'm the lead developer. I can go into this a bit more when I get from an appointment if people are interested.
- joecool1029 10mo agoI’m interested. Mainly to update the documentation on it for Gentoo, people have asked about it over the years. Also, TIL it appears HN has a sort of account dormancy status it appears you are in.
- rapier1 10mo agoFor Gentoo I should put you in touch with my co-developer. He's active in Gentoo and has been maintaining a port for it. I'll point him at this conversation. That said, documentation wise, the HPN-README goes into a lot of detail about the HPN-SSH specific changes. I should point out that while HPN-SSH is a fork we follow OpenSSH. Whenever they come out with a new release we come out with one that incorporates their changes - usually we get this out in about a week.
- nhatcher 10mo agoIf folks find this interesting, maybe also mosh[1] is for you. Different trade offs. [1]: https://mosh.org/ https://mosh.org/
- freedomben 10mo agoThis is cool very cool and I think I'll give it a try, though I'm wary about using a forked SSH so would love to see things land upstream. I've been using mosh now for over a decade and it is amazing. Add on rsync for file transfers and I've felt pretty set. If you haven't checked out mosh, you should definitely do so!
- chrisweekly 10mo agowary (cautious or skeptical), not weary (tired)
- actionfromafar 10mo agoAt this point, maybe both. :) Can we have a portmanteau?
- freedomben 10mo agoIndeed! I meant wary, but both kind of fit :-D
- freedomben 10mo agoHeh, thank you! Edited
- ollybee 10mo agoIt's not clear if you need it on both ends to get an advantage?
- rapier1 10mo agoThe bottleneck in SSH is entirely on the receiving side. So as long at the receiver is using HPN-SSH you will see some performance improvements if the BDP of the path exceeds 2MB. Note: because of changes made to OpenSSH in 8.8 the maximum buffer with OpenSSH as the sender is 16MB. In an HPN to HPN connection that maximum receive buffer is 128MB.
- baden1927 10mo agoThe contracting activity in terms of rsync and async, where SFTP is secure tunneling, either with SSH or OpenSSH, which -p flag specifies as the port: 22, but /ssh/.configuring 10901 works for TCP.
- tristor 10mo agoI don't think it comes as a surprise that you can improve performance by re-implementing ciphers, but what is the security trade-off? Many times, well audited implementations of ciphers are intentionally less performant in order to operate in constant time and avoid side channel attacks. Is it even possible to do constant time operations while being multithreaded? The only change I see here that is probably harmless and a speed boost is using AES-NI for AES-CTR. This should probably be an upstream patch. The rest is more iffy.
- rapier1 10mo agoThe parallel ciphers are built using OpenSSL primitives. We aren't reimplementing the cipher itself in anyway. Since counter ciphers use an atomically increasing counter you can precompute the blocks in advance. Which is what we do - we have a cache of ketstream data that is precomputed and we pull the correct block off as needed - this gets around the need to have the application compute the blocks serially which can be a bottleneck at higher throughput rates. The main performance improvement is from the buffer normalization. This can provide, on the right path, a 100x improvement in throughput performance without any compromise in security.
- joecool1029 10mo agoThis has been around for years (like at least mid-2000’s). Gentoo used to have this patchset available as a USE flag on net-misc/openssh, but some time ago it was moved to net-misc/openssh-contrib (also configurable by useflag). There are some minor usability bugs and I think both endpoints need to have it installed to take advantage. I remember asking ages ago why it wasn’t upstreamed, there were reasons…
- rapier1 10mo agoto be honest, there was a period of time in about 2010 or 2012 where I simply wasn't maintaining it as well as I should have been. I wouldn't have upstreamed it then either. That's changed a lot since then. As an aside - you only really need HPN-SSH on the receiving side of the bulk data to get the buffer normalization performance benefits. It turns out the bottleneck is almost entirely on the receiver and the client will send out data as quickly as you like. At least it was like that until OpenSSH 8.8. At that point changes were made where the client would crash if the send buffer exceeded 16MB. So we had to limit OpenSSH to HPN-SSH flows to a maximum of 16MB receive space. Which is annoying but that's still going to be a win for a lot of users.
- nickcw 10mo agoThe fact that sftp is not the fastest protocol is well known by rclone users. The main problem is that it packetizes the data and waits for responses, effectively re-implementing the TCP window inside a TCP stream. You can only have so many packets outstanding in the standard SFTP implementation (64 is the default) and the buffers are quite small (32k by default) which gives a total outstanding data of 2MB. The highest transfer rate you can make depends on the latency of the link. If you have 100 ms of latency then you can send at most 20 MB/s which is about 200 Mbit/s - nowhere near filling a fast wide pipe. You can tweak the buffer size (up to 256k I think) and the number of outstanding requests, but you hit limits in the popular servers quite quickly. To mitigate this rclone lets you do multipart concurrent uploads and downloads to sftp which means you can have multiple streams operating at 200 Mbit/s which helps. The fastest protocols are the TLS/HTTP based ones which stream data. They open up the TCP window properly and the kernel and networking stack is well optimized for this use. Webdav is a good example.
- riobard 10mo ago"(sftp) packetizes the data and waits for responses, effectively re-implementing the TCP window inside a TCP stream." why is it designed this way? what problems it's supposed to solve?
- Veserv 10mo agoBecause that is a poor characterization of the problem. It just has a in-flight message/queue limit like basically every other communication protocol. You can only buffer so many messages and space for responses until you run out of space. The problem there is just that the default amount of buffering is very low and is not adaptive to the available space/bandwidth.
- rapier1 10mo agoYeah, it's an issue because there is also the per channel application layer flow control. So when you are using SFTP you have the TCP flow control, the SSH layer flow control, and then the SFTP flow control. The maximum receive buffer ends up being the minimum of all three. HPN-SSH (I'm the dev) normalizes the SSH layer flow control to the TCP receive buffer but we haven't done enough work on SFTP except to bump up the buffer size/outstanding requests. I need to determine if this is effective enough or if I need some dynamism in there as well.