There is one correction, in-line. > Kris Deugau: > > We found that DNS-based round-robin strategies didn't actually balance > > the load very well. > > This looks like the same problem that was found (and solved) with > Postfix outbound connection caching; if a destination host became > slow for whatever reason, it became a fatal attractor for connections. > > For example, twice as slow -> twice as many clients. > > With outbound connection caching, this was solved in the Postfix > SMTP client, by limiting the total duration of an SMTP session. > > For example, twice as slow -> half the number of sessions
Correction: half the number of deliveries. > With inbound SMTP, it is not possible to tell clients to go somewhere > else except by interposition, for example with an layer-3 proxy > (nginx), with a layer 2 switch/nat/etc, or by interposing at the > DNS level (adjust DNS replies according to server load). I don't > know if the last is in use for SMTP. > > Wietse >
