From: Dana Quinn (danaIZZATnextbus.com)
Date: Wed Jun 25 2003 - 13:11:20 EDT
I implemented a partial global load balanced site a few years
ago - late fall 2000 into 2001, and I think the limitations
were fairly well understood then. We used the F5 solution, and I
remember having detailed discussions with some of their
tech people about DNS caching issues, including DNS caching
problems in various versions of Internet Explorer.
I said a 'partial' site because the global load balancers
were mainly used to do a datacenter move -
it allowed us to slowly shift traffic over a couple months.
We saw various client systems that continued to cache our old
DNS results one way or another for weeks, even months. :(
Anyway, I agree that using some sort of BGP-based multi-homing
is a better way to survive most common failures, but setting
up and running BGP requires a strong committment in staff
and equipment. The little content company I worked for at the
time I worked in this realm wasn't too interested in going that
Does anyone on list have experience with using network
service providers that help to manage BGP-like multi-homing
for web sites? I'm thinking of InterNAP, mainly, or other
companies that provide similar services. I'd be interested
in hearing how they work out for people.
David Taylor wrote:
>> May I ask how you moved away from the GSLB solution? We do it to
>> get around points of failure like the network connection/ISP,
>> and other single points of failure at one site.
> We did indeed go for a failover situation and built our primary site to
> be as resilient as possible. It gave us quite a shock to discover the
> limitations of GSLB at the time (probably 2 or 3 years ago now) as we
> had largely implemented a hosting environment that relied on GSLB - the
> failover approach is nowhere near as elegant as an active / active
> At the time, the DNS caching limitation of GSLB did not seem to be
> widely recognised.
> Our ultimate approach was to accept that in the event of total loss of
> the primary site, our service desk would need to anticipate a high
> volume of customer calls and would need to be able to manage customers
> who required assistance with refreshing DNS caches. Not ideal, but for
> the company an acceptable solution.
> In hindsight. had we been aware of the GSLB issues, we may well have
> designed our environment using our own physically seperate datacenters
> and BGP with upstream ISPs. In my view, for ultimate availability, IP
> addresses must be completely static to the customer, regardless of what
> goes on in the hosting network.
> Surf the net and talk on the phone with Xtra Jetstream IZZAT
> http://www.xtra.co.nz/products/0,,5803,00.html !
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Dana Quinn, danaIZZATnextbus.com NextBus Information Systems (510) 420-3117
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