[Cerowrt-devel] High Performance (SSH) Data Transfers using fq_codel?

Dave Taht dave.taht at gmail.com
Thu Nov 13 22:11:41 EST 2014

One thing the HPC crowd has missed is that in their quest for big
buffers for contenental distances, they hurt themselves on shorter

... and also that big buffers with FQ on them works just fine in the
general case.

As always I recomend benchmarking - do a rrul test between the two
points, for example, with their recomendations.

On Fri, Oct 17, 2014 at 4:21 PM, Frank Horowitz <frank at horow.net> wrote:
> G’Day folks,
> Long time lurker. I’ve been using Cero for my home router for quite a while now, with reasonable results (modulo bloody OSX wifi stuffola).
> I’m running into issues doing zfs send/receive over ssh across a (mostly) internet2 backbone between Cornell (where I work) and West Virginia University (where we have a collaborator on a DOE sponsored project. Both ends are linux machines running fq_codel configured like so:
>         tc qdisc
>         qdisc fq_codel 0: dev eth0 root refcnt 2 limit 10240p flows 1024 quantum 1514 target 5.0ms interval 100.0ms ecn
> I stumbled across hpn-ssh <https://www.psc.edu/index.php/hpn-ssh> and —  of particular interest to this group — their page on tuning TCP parameters:
> <http://www.psc.edu/index.php/networking/641-tcp-tune>
> N.B. their advice to increase buffer size…
> I’m curious, what part (if any) of that advice survives with fq_codel running on both ends?
> Any advice from the experts here would be gratefully received!
> (And thanks for all of your collective and individual efforts!)
> Cheers,
>         Frank Horowitz
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Dave Täht


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