Date: Sat, 15 Sep 2001 22:28:44 +0930 From: Andrew Reid <andrew.reid@plug.cx> To: Fabrizio Ravazzini <freefabri@yahoo.it> Cc: freebsd-isp@freebsd.org Subject: Re: Mail Server - Round Robin Load Distribution Message-ID: <20010915222844.A6415@plug.cx> In-Reply-To: <20010915080113.985.qmail@web20101.mail.yahoo.com>; from freefabri@yahoo.it on Sat, Sep 15, 2001 at 10:01:13AM %2B0200 References: <20010915080113.985.qmail@web20101.mail.yahoo.com>
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On Sat, Sep 15, 2001 at 10:01:13AM +0200, Fabrizio Ravazzini wrote:
> I want to make this cluster using DNS-RoundRobin.
> Reading the book DNS&BIND (O'Reilly) page 274, if I
> insert two A-Records with two CNAME I can make
> the round Robin, but this for ftp,http or whatever
> server,but I think NOT Mail Servers.
Hrm, your interpretation seems a little weird. Basically, you'd do
something like this to achieve "load balancing" through DNS:
domain.com. IN MX 10 mail
mail IN A 1.2.3.4
mail IN A 1.2.3.5
Basically, what would happen in the case of an email being sent to
joe@domain.com is:
o ) Remote SMTP server queries DNS server for domain.com to find the
MX host.
o ) Remote SMTP server queries DNS server for domain.com to find the
IP Address for mail.domain.com.
o ) DNS server for domain.com responds to remote SMTP server with
either 1.2.3.4 or 1.2.3.5, based on the method of "load
distribution" employed by BIND.
> So,the question is, can I still have load distribution
> with a mail server?
Most certainly. Remember, SMTP is just another port on your
server. Round Robin DNS is just one form of load balancing. Other
methods might include using software such as balance, or another piece
of software by the makers of vmailmgr. Then again, you could shell out
many thousands of dollars and purchase a commercial load balancing
switch.
> Suppose that the service domain is mail.com, so you
> can send mail for example to john@mail.com
> and the two machine of the cluster are:
> one.mail.com ( Ip: A.B.C.D )
> two.mail.com ( Ip: X.Y.Z.K )
[ ... ]
> In the second case I don't have any Load Distribution,
> all the traffic goes to the "one.mail.com"
> till it goes down and that's not what I want.
Perhaps you need something like balance which includes the ability to
cater for failures. That'll take care of the load balancing and the
redundancy in the one operation. Bear in mind that you'd then need a
machine which you could use for the purpose of running balance on. It
also becomes a single point of failure.
- andrew
--
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cout << "Andrew Reid -- andrew.reid@plug.cx" << endl ;
cout << "Cell: +61 401 946 813" << endl;
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}
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