Web site failover

[Jeff Lasman]

On Tuesday 10 February 2004 05:43 am, Ned Trilby wrote:

> How can I set up a failover (within 4 hours) of a website? My site
> "TEST111.com" is running in "SITEA" with ISPA as the ISP. If SITEA
> burns down I have a standby machine in SITEC with a connection to
> ISPB. Can ISPB take over traffic for "TEST111.com"? How is this
> achieved? I would only see my standby machine connected to the
> Internet if the original machine in SITEA fails.

Here's a recipe for quick-and-dirty failover protection:

First:

Set your domain to use two nameservers, for example, ns1.example.com and 
ns2.example.com, with ns1.example.com pointing to an IP# resolving to 
the machine at ISP1 and ns2.example.com pointing to an IP# resolving to 
the machine at ISP2.

Both machines must be running a nameserver.

Each nameserver must be set up as a master for the domain and not a 
slave, and must resolve the website name (for example www.example.com 
and perhas example.com as well) to itself.

So you'll need two copies of the site, one on the machine hosted at ISP1 
and one on the machine hosted at ISP2.

If both machines are active at the same time then some hits will go to 
the machine at ISP1 and some to the machine at ISP2.  This will work 
fine if the sites are static sites.  If only one machine is connected 
to the net at a time, then that machine will get all the hits.  
(Visitors to the site at the time of failure, and others using the same 
nameservers, won't be able to see the site for the TTL time, so you'll 
probably want to keep that as short as possible.)

If the sites are not static sites, then your scenario in which you only 
turn on the standby system after the main system fails will work, but 
unless you've kept the sites synchronized, the site the visitors see on 
the standby system might not be the same site they saw on the main 
system.

While I'm sure a bunch of people will come up with a lot of reasons why 
this isn't a good idea, it will do what you want to do as inexpensively 
as it can be done.

Jeff
-- 
Jeff Lasman, nobaloney.net, P. O. Box 52672, Riverside, CA  92517 US
Professional Internet Services & Support / Consulting / Colocation
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