Date: Fri, 14 Feb 2003 14:03:47 +0100 From: Brad Knowles <brad.knowles@skynet.be> To: Terry Lambert <tlambert2@mindspring.com> Cc: Brad Knowles <brad.knowles@skynet.be>, Rahul Siddharthan <rsidd@online.fr>, freebsd-chat@freebsd.org Subject: Re: Email push and pull (was Re: matthew dillon) Message-ID: <a05200f12ba7298a80b59@[10.0.1.2]> In-Reply-To: <3E4C9612.2777D62E@mindspring.com> References: <20030211032932.GA1253@papagena.rockefeller.edu> <a05200f2bba6e8fc03a0f@[10.0.1.2]> <3E498175.295FC389@mindspring.com> <a05200f38ba6f51f20eff@[10.0.1.2]> <3E49C434.D8D497EE@mindspring.com> <a05200f44ba6fe5dff1a0@[10.0.1.2]> <3E4A83BC.8A15E7C3@mindspring.com> <a05200f4fba70847460b3@[10.0.1.2]> <3E4B12F5.2608BBB@mindspring.com> <a05200f5cba7146e25655@[10.0.1.2]> <3E4BB64E.A9AEED28@mindspring.com> <a05200f06ba71eac7fe1c@[10.0.1.2]> <3E4C9612.2777D62E@mindspring.com>
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At 11:09 PM -0800 2003/02/13, Terry Lambert wrote:
> No... but does proxy really solve anything, then, more than
> a DNS rotor solves? All it really does is add a single point
> of failure. Unless you can target a subset of back end content
> servers, you might as well use DNS round-robin. Using a proxy
> implies the back end replica problem is *already* solved.
Yes, the proxy does solve the domain problem. The user logs in
with "user@domain", the proxy looks this up in the LDAP database,
which then tells it which back-end server to contact. You can
decide, on a user-by-user basis, which back-end server they will be
using for their mail. If one back-end server gets overloaded, you
can choose individual users to shift off to another machine.
Besides, you don't use just one front-end proxy. You use them in
sets of at least two, and you drop L3/L4 load balancing switches in
front of them, and the L3/L4 switches get DNS round-robin. The
switches handle balancing the connection load, and the proxy+database
handles the balancing of user mailboxes over the set of potentially
asymmetric back-end servers.
The issue of replication is a totally different matter.
> Maybe I should say "doesn't deal with LDAP the way it should"
> instead?
In what way?
--
Brad Knowles, <brad.knowles@skynet.be>
"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety."
-Benjamin Franklin, Historical Review of Pennsylvania.
GCS/IT d+(-) s:+(++)>: a C++(+++)$ UMBSHI++++$ P+>++ L+ !E-(---) W+++(--) N+
!w--- O- M++ V PS++(+++) PE- Y+(++) PGP>+++ t+(+++) 5++(+++) X++(+++) R+(+++)
tv+(+++) b+(++++) DI+(++++) D+(++) G+(++++) e++>++++ h--- r---(+++)* z(+++)
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