[CentOS] Load balancing...

Les Mikesell lesmikesell at gmail.com
Fri Mar 4 04:14:21 UTC 2011

On 3/3/11 7:56 PM, Sean Hart wrote:
>>>> Hi Sean,
>>>> Can you explain as I may be planning this for a site.
>>>> So if I have 2 identical servers, each with there own IP, how will
>>>> one
>>>> of them going down cause issues?
>>>> I'm assuming multiple A records for the same host will be handled
>>>> fine
>>>> by the client lookup?
>>> example.com resolves to:
>>> host1.example.com - A.B.C.D
>>> host2.example.com - W.X.Y.Z
>>> 1. Client performs DNS lookup and gets pointed to host2. All is well.
>>> 2. host2 goes down. DNS for example.com still resolves to host2,
>>> which is unreachable. Site is down.
> Yeah, what they said!  I've done a few of these myself if you want to
> chat further off the list about your specific needs and so forth.  I
> don't contract or anything, but I'm down to give advice.

Browsers actually handle this pretty well.  If you give out multiple IPs and 
some are unreachable, most browsers will almost instantly connect to one one 
that works.  And they'll recover even if one goes down after you have a 
connection.  This only works if you give out all of the addresses in the first 
place, though.  You can't count on changes to DNS to take effect quickly.

   Les Mikesell
    lesmikesell at gmail.com

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