How websites are mirrored ...i Mean one of my frend have a server in India but the down time at his server is at times high due to backbone problem. Now i wonder if he could offer his clients mirrored hosting in US so that if the link of India is down the traffic may be directly routed to US based host ...is it possible ??? how is it done ..Please enlighten me ..with all your knowledge :stickout

A cheap alternative way is to do round robin DNS. Basically setup multiple A records on the DNS server so either or will come up. This probably won't help if the DNS server is located on the same network that goes down due to high latency. Other than that, he can have a splash page located at another geographic loation which will prompt the user to choose between a US mirror and an India mirror.

thanks teck,

But the problem is if he chooses to host a spalsh page at the other geographic location the other host may or may not allow him to run his DNS now that would mean his domains reflect the DNS of the other host ...is it so ??? and if that happens then he loses his id ..??I'm not sure though if it is so ...

You might want to inquire about their nameservers and how they are set up. I would think that if both nameservers (or more) are on seperate networks, seperate backbones, even seperate sides of the globe, your main nameserver can point to your normal host/site while the backup server can point to the alternate host/site. That way, if the normal site goes down (and I'm going to assume the nameserver goes alone with it), the domain will default to the backup nameserver which is pointing to the alternate host with the alternate site. Once the domain finishes with the backup nameserver it'll look for the main nameserver again. If it finds it, that probably means your site is up too, which means you're back in business.

Of course, this depends entirely on how you set things up, and I have never tried this myself, but I think it would work.

If you use a splash page, you wouldn't need to do round robin DNS. All you need is a static page with 2 links..one to USA, one to India. You would want round robin DNS only if you want the mirrors to be transparent when a user goes to your websiite

The problem with round robin DNS is that DNS doesn't check to see if a server is up. So if you round robin your DNS and the site in India goes down half your visitors will still try to go to the downed site.

There are two ways to get around this that occur to me:

1. a Globally Load Balanced Solution (prolly 'spensive).
2. I've never tried this, but you might be able to use DDNS to update the nameservers, so that the server that is up is the only one that people can get to...not sure how the details would work...I've have to hammer it out in more detail...and it would also only work in a failover type state (ie server in US only activated if there is a failure in India.

Originally posted by uuallan
The problem with round robin DNS is that DNS doesn't check to see if a server is up. So if you round robin your DNS and the site in India goes down half your visitors will still try to go to the downed site.
I'm not exactly sure what "round robin DNS" is, but if you are referring to my suggestion, I was assuming that the site and the nameserver were on the same network and possibly the same server that is down. Of course, if the nameserver and web server are two different servers and the web server goes down while the nameserver stays up, then my suggestion goes right out the window. :)

Round robin DNS is the practice of mapping the same subdomain to multiple IP addresses. If I wanted to round robin www.domain.com, the zone entries would look something like this:


www IN A 10.10.10.1
www IN A 10.10.10.2
www IN A 10.10.10.3
www IN A 10.10.10.4


The way the DNS specification works, is that the first person who queries the DNS server looking for the address for www.domain.com will be sent to 10.10.10.1 the second person will be sent to 10.10.10.2, and so on.