UDT4 and rsync? support to socket.c?

Jan Wagner jan.wagner at iki.fi
Wed Mar 24 14:19:50 MDT 2010

Jamie Lokier kirjoitti:
> Jan Wagner wrote:
>> Hi, has anyone of the devels considered adding UDT4 fast reliable udp 
>> transport to socket.c, as a user-selectable alternative to using default 
>> slow TCP?
>> It could give a 4 to 10-fold throughput improvement to rsync speed over 
>> wide area networks.
> If you're seeing that, you must be using an old OS at one/both ends,
> or poor TCP settings, or a broken router, or have a very unreliable link.
Seeing it, with 10G links to the Internet and 1G/10G machines on the 
links, in Europe and over different continents, lots of small files (few 
gbyte per file), reasonably new Ubuntu/Debian typically at the ends, 
NICs typically Myrinet and Chelsio, single computer disk subsys' can 
sustain about 6 Gbps.

Sure, on home cable and short distances TCP at least ramps up reasonably 
fast and rate recovery does not take ages and it fares pretty well vs 
UDP rates. Can't get quite the same out of TCP on 10G (except locally). 
In some cases non-ssh rsync throughput is closer to 100Mbps (was on 
Japan-Finland i think) than to 500..900Mbps/~1G nic/udp/udt4/tsunami rate.
> Anyway, if you really want to use UDT4, it is probably better to use a
> generic TCP<->UDT4 proxy and point rsync to that.
Thanks, hmm, actually there seems to be 
http://sourceforge.net/projects/udtgate/   I'll give it a go...!

 - Jan

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