Your Blog, Custom Domains, And The Quadruplet Google Apps Servers

Some people can't see the forest, for the trees. Occasionally, we see a perplexed query from a blogger, seeking to publish to a custom domain.

Google wants us to repeat the same IP address 4 times?
216.239.32.21
216.239.34.21
216.239.36.21
216.239.38.21
Uh, aren't they're the same?

Like quadruplets (newly born human children), you may need name tags to distinguish one server from the other. But, if you look closely enough, no, they aren't the same.

mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

The server "ghs.google.com" is a DNS array, with multiple levels and multiple redundant parts. We use "ghs.google.com" to resolve the "www" alias of the domains, using a "CNAME" referral. Most custom domains are published to the "www" alias, so "ghs.google.com" is massively robust, with redundant parts.

If we use a similar "CNAME" referral to resolve the domain root, aka "naked domain", we could interfere with resolution of email, FTP, and other possible auxiliary domain services hosted, by the registrar. Instead, we use multiple "A" referrals, mutually redundant.

Long ago, until November 2008, we used "64.233.179.121", "66.249.81.121", and "72.14.207.121", which were triple mutually redundant equivalents of "ghs.google.com". And, you could easily see "64.233.179.121", "66.249.81.121", and "72.14.207.121" as different IP addresses.

mydomain.com.  3600 IN A 64.233.179.121
mydomain.com.  3600 IN A 66.249.81.121
mydomain.com.  3600 IN A 72.14.207.121
www.mydomain.com. 3600 IN CNAME ghs.google.com.

Now, we use the quadruple mutually redundant configuration. And, "216.239.32.21", "216.239.34.21", "216.239.36.21", and "216.239.38.21" are different IP addresses, though they look the same - if you don't look closely enough.

mydomain.com.  3600 IN A 216.239.32.21
mydomain.com.  3600 IN A 216.239.34.21
mydomain.com.  3600 IN A 216.239.36.21
mydomain.com.  3600 IN A 216.239.38.21
www.mydomain.com. 3600 IN CNAME ghs.google.com.

So, why 4 servers? Won't 1 do? Generally, yes. But not 1 server is going to be 100% reliable, or last forever. Every computer ever made, like every human born, will die, one day. Your blog (domain) depends upon DNS, to resolve its address. If you specify 1 server, and that 1 server goes down, your domain will be out of service.

As I wrote above, "ghs.google.com" is a redundant server array. But we have to use a "CNAME" to reference "ghs.google.com", and we can't always use a "CNAME".

www.mydomain.com. 3600 IN CNAME ghs.google.com.

When we have to use an "A" referral to define the domain root, we can't use "ghs.google.com". Here, Google provides 4 mutually redundant single servers, for us to access in a round robin array. If any 1 server becomes overloaded or goes out of service, and doesn't respond to a DNS query, the DNS resolver will try the next one defined - if there is another defined. If your domain uses just 1 server, and that 1 server goes down, your domain goes out of service. Your readers will see, yet again

404 Server Not Found

But wait - - there's more. Since Google has 4 servers available, if only 1 is out of service, they won't regard that as a major emergency. They still have 3 servers, and nobody is losing sleep. Except, of course, you. Google will repair or replace their 1 down server, as convenient to them. Not convenient to you? Sorry.

With an asymmetrical configuration, you may not publish to the domain root. Your only valid choice is to publish to "www.mydomain.com", and select "Redirect mydomain.com to www.mydomain.com". If you publish to "mydomain.com", you will eventually see

Another blog is already hosted at this address.

or

Blogs may not be hosted at naked domains.

If you want to publish your blog to a custom domain using an ASymmetrical configuration, always publish to "www.mydomain.com", not to "mydomain.com". If you want to publish to "mydomain.com", you'll have to use a Symmetrical DNS configuration, and risk losing services hosted by your registrar. If you go with the first option, you will need all 4 servers, if you want a reliable and supported custom domain.

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