2010/2/16 donovan jeffrey j <dono...@beth.k12.pa.us>: > > On Feb 16, 2010, at 10:39 AM, Massimo Nuvoli wrote: > >> donovan jeffrey j ha scritto: >>> >>> On Feb 16, 2010, at 8:09 AM, aa wrote: >>> >>>> Someone advised me to insert in the DNS zone a list of MX records >>>> defined with the same level of priority so the DNS server will choose >>>> one of them without invoking always the same mail server.... >>>> It could be an idea, in my opinion, but I'd prefer a "less random" >>>> solution and a more scientific one.... >>> >>> very easy for smtp relays. >>> smtp1 >>> smtp2 >>> create a dns name smtp, and your system will round robin query for the >>> next available server. >> >> DNS round robin is bad, it works but is defective for real load >> balancing. The client choose the IP to use, this is "random", and >> after can use the same ip for a while... this is not random. >> >> The real solution is lvs or keepalived, the choice of the node is done >> by the load balancer... >> >> Bye. >> <massimo.vcf> > > I wouldn't say it's bad, it's just cheap. Of course a load balancing switch > can be purchased $
Well, It is bad because server (client) can cache ip address for long time and then one of your smtp server fails. It can take long time before server gets ip address of working smtp server.. -- Eero
