[CentOS] Load balancing...

[Nico Kadel-Garcia]

On Thu, Mar 3, 2011 at 7:25 PM, Ryan Ordway <rordway at oregonstate.edu> wrote:
> On Mar 3, 2011, at 4:12 PM, aurfalien at gmail.com wrote:
>
>>> Round robin DNS would balance load, but will cause problems if one of
>>> them goes down.
>>
>> 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.
>
> Now, you can work around this by using a HA/failover system like heartbeat to have host1 and host2 communicating with each other and if one host goes down the other automatically takes over its IP address(es) and services. If you have control over your own DNS you can manage your zone's Time To Live so that records are less aggressively cached, etc.

Or "wackamole", which I've used in the past very successfully.

But the high video and high MySQL use are, themselves, issues. One of
the keys is to distribute the *content* to distinct hosts. Video to
something optimized for video, MySQL to a host right next to the
database server, flat text and simple images wherever possible, and
avoid Javasript oddities which slow down everything and cause problems
for ADA complicance.

If you can view the website with Lynx, you're probably doing the right
things to reduce unnecessary and extraneous *content* that will burden
your server.