[CentOS] High Availability using 2 sites

Bryan J. Smith thebs413 at earthlink.net
Fri Jan 6 00:48:26 UTC 2006


Les Mikesell <lesmikesell at gmail.com> wrote:
> You can if you always offer distributed locations and
> let the client choose the address.

The problem with that is it is too arbitrary.

> Web browsers already do that.

I think we disagree there.  And I think you are stretching
some things to fit web browsers that are simply not true.

> I'm not sure what you are talking about. We have two
> colo sites with an assortment of web and proprietary
> services.  No ADS in sight.

Okay, no ADS.  I was waiting for that confirmation.

> I have F5 3dns boxes as the primary DNS servers but
normally
> let them give out both addresses for all services, all the
> time.

Once again, you're looking at it from your perspective very
close to the authority.  That's completely different than any
arbitrary user who may be several non-authoritative
resolutions away.

> IE mostly just works.  Our own client software takes care
of
> failover using the addresses supplied by DNS. It has its
own
> heartbeat on the server connection and will reconnect
anytime
> it notices a problem with the connection, trying every
> address in the list.  When it reconnects it refreshes
certain
> things from the new server connection.

Whoa!  Whoa!  Whoa!!!

You're talking about heartbeats and other "keep alives" that
are not common to web servers with many, many clients from
many, many web clients.  You're almost approaching a stateful
client/connection when you do such, along with the
associated, added traffic.

So, again, your context is _very_different_ than what I
understand the need to be here for generic web servers and
browsers.
> Try it.  If you are resolving names with netbios you might
> see something different.

*SMACK*  ;->  Right there, you don't understand a thing about
how ADS-DNS works.  No offense.  ;->

It is _not_ NetBIOS.  MS IE does some nasty stuff when it has
ADS.  MS IE does some stupid stuff when it doesn't as well.

Anyone who has maintained a very large enterprise network
will tell you about all of the nasty and/or stupid stuff MS
IE does for both intra and Internet resolution and requests.

I've had to write some really "fun" GPOs as a result.

> Being able to get all the addresses from multiple A
> records doesn't have anything to do with hold downs.

You should read up on how the Windows resolver works as well
as how MS IE operates both with and without ADS-integrated
DNS.  ;->



-- 
Bryan J. Smith     Professional, Technical Annoyance                      b.j.smith at ieee.org      http://thebs413.blogspot.com
----------------------------------------------------
*** Speed doesn't kill, difference in speed does ***



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