Re: 2 Colo's

Hi,

 

I agree this can of things can happen and this are the reasons I told in my previous mail that ADC vendors are aware regarding DNS-based GSLB problem and we are offering other alternatives to overcome such problem. This situations are documented and here you have an example from the Radware AppDirector User Guide:

---- snip ----

DNS Fallback

When DNS Redirection is enabled, you can define whether DNS is the only

redirection method for this farm, the primary redirection method or just one of

the available redirection methods for the farm. If DNS is the primary redirection

method, backup redirection methods can be configured for cases when the

application request reaches a site where there are no servers available.

---- snip ----

 

Of course in a User Guide you will not find all the situations that can be happen but you have explanations to configure the device for this can of situations, this is the basic spirit of this forum, sharing experiences and exchange information to know LB situations, needs and solutions. So now people is aware from the pure DNS-based GSLB and the other options available in the market.

 

Thanks,

Juan Carlos

 

De: [email protected] [mailto:[email protected]] En nombre de Surya ARBY
Enviado el: viernes, 29 de mayo de 2009 8:04
Para: Load Balancing Mailing List
Asunto: Re: [load balancing] 2 Colo's

 

Hello.

In real world implementation, the TTL issue (dead A record) is already present in the Internet (mostly in Asia, but also in Europe), I faced it during the migration of one site to another, a lot of users coming from a major local ISP were directed on the "old" IP address by their resolvers for days. I don't think it's acceptable for critical web sites and if it happens in the real world, the article is not just "something alarmist based in theoretical situations".

Of course DNS-based GSLB solutions are not perfect, but there is not a single mention of the associated caveats (TTLs not honored, source-ip dns persistance broken, shuffled ordered lists...) in all products documentations I could read (except for the biaised DNS proximity based on the client's resolver, not the client itself). How can a user tune it's config correctly if he doesn't know the associated problems ?

regards,

Surya

--- En date de : Ven 29.5.09, Juan Canete <[email protected]> a écrit :


De: Juan Canete <[email protected]>
Objet: Re: [load balancing] 2 Colo's
À: "Load Balancing Mailing List" <[email protected]>
Date: Vendredi 29 Mai 2009, 0h35

Hi,

 

My name is Juan Carlos Cañete (Radware-Alteon Technical Consultant for EMEA) and I’m very happy to see how this article comes now and then to the nowadays. In this forum I have seen the people “hate” this article but for me it is perfect because it has helped me a lot of times to show customers that the problem described at it can be overcome with ADC solutions.

 

I don’t know if you are using ADC solution in your actual facility but I’m sure you are looking for fast service fail over, optimization and high availability for your applications in case of failure or disaster. DNS resolution is only the first tier for a GSLB and you must be able to use other tiers, like the article describes, in order to guarantee a problem with the DNS resolution. The final thought from the article can be summarize to avoid using multiples sites because there is not a 100% perfect solution for it. I can’t agree in this argument because if you have only one site you can’t guarantee your applications to be available 24x7. In the same article there are examples to kill the GSLB like DoS attack to one site, OK, what will happen if you have only one site and you are under DoS attack?

 

ADC solutions can help a lot under such situations because in its responses can redirect the users to other sites that are not congested, I mean, under attack and your clients will be available to get access to your applications/services. The customer experience and the amount of GSLB developed, not only by Radware, it is the best example that the article is just something alarmist based in theoretical situations.

 

My two cents,

Juan Carlos 

 

De: [email protected] [mailto:[email protected]] En nombre de Dane Ruyle
Enviado el: miércoles, 27 de mayo de 2009 21:01
Para: Load Baalancing
Asunto: [load balancing] 2 Colo's

 

Hi all,
 
I'd like to hear your input on the best way to bring a second collocation facility online.  We are a SAAS company.  Basically, our service is all tied to a domain name; the www record.  
 
It was my intent to use 2 A records to the WWW lookup. Then, use GSLB to control the traffic.    
 
This works fine when both sites are up and running, but what happens when one goes down - rely on the built-in failover mechanism is DNS (the second A record)?
 
There's a GSLB Page of Shame http://www.tenereillo.com/GSLBPageOfShame.htm <http://www.tenereillo.com/GSLBPageOfShame.htm> 
 
Would love to hear your input as I am going to be bringing a second one online.
 
Thanks for your time,
dane
 

________________________________

Windows Live™: Keep your life in sync. Check it out. <http://windowslive.com/explore?ocid=TXT_TAGLM_BR_life_in_synch_052009> 


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