Geographical Load Balancing

Ryan Byrd ryanbyrd at gmail.com
Wed Nov 11 16:25:10 MST 2009


having a super short TTL is a great way to overload your DNS servers and
clients don't have to honor the TTL anyway and will often cache the records.
IE caches records for 30 mins, I believe, for example.

On Wed, Nov 11, 2009 at 3:50 PM, Steven Alligood <steve at bluehost.com> wrote:

> On 11/11/2009 03:35 PM, William Attwood wrote:
>
>> On Wed, Nov 11, 2009 at 3:27 PM, Steven Alligood<steve at bluehost.com>
>>  wrote:
>>
>>
>>
>>> On 11/11/2009 03:19 PM, William Attwood wrote:
>>>
>>>
>>>
>>>> Hello--
>>>>
>>>>    How does one accomplish geographical load balancing? With that in
>>>> mind,
>>>> what about geographical failover?  Example, I have a data center (DC) in
>>>> Dallas, and another in Salt Lake.  How do I re-direct traffic if Dallas
>>>> goes
>>>> offline?
>>>>
>>>>    Just a project I'm diving into.  colo-specific load balancing and
>>>> failover is accomplished, now we need to protect against the data center
>>>> going offline, and speed of access to machines.  I see how I can do
>>>> geographical failover with a geographical load balancer, however, do I
>>>> need
>>>> 2 geographical load balancers if one of them goes offline?
>>>>
>>>>    Has someone here worked on a project of this magnitude?
>>>>
>>>>
>>>>
>>>>
>>>>
>>> It';s been several years since I have set that up, but the old alteons
>>> (now
>>> owned by nortel) would do geographical load balancing with one in each
>>> location.
>>>
>>> Basically, you setup your auth dns to point to each location, with any
>>> subdomain in DNS delegated to the load balancer.  It would then give out
>>> dns
>>> based on which one it found to be quicker, etc, and in an outage would
>>> give
>>> just itself out for it's local farm.
>>>
>>> Of course, if you are doing IPv6, check out the anycast stuff.  Quite
>>> amazing.
>>>
>>> -Steve
>>>
>>>
>>>
>>
>> If one site goes offline, won't that mean 50% of my traffic also goes
>> offline, depending on which IP DNS feeds back?  I may have misunderstood
>> you.
>>
>>
>>
> No, the dns for those particular subdomains have very short TTLs (like, 5
> seconds), so they expire quickly and have to be looked up again.  So if your
> site goes down between one web page serve and the next, it gets the DNS
> entry for the site that is still online.
>
>
>
>
>
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