Multiple server query

[inky]

I currently have several domains hosted with another provider but I have used up all my space and I'm reluctant to get any more with them. I still have 10 months or so prepaid with them so will not be moving my existing sites...yet. I have some new clients lined up so need somewhere for them to live.

I currently have ns1.mydomain.com & ns2.mydomain.com setup with my original host (lets call this server A).
If I were to take a package out here could I set my nameservers to ns3.mydomain.com & ns4.mydomain.com (lets call this server B).

I'm assuming I could set up new clients on server B and simply set the nameservers for their domain to ns3 & ns4.

I would like to have a 'Site temporarily unavailable' page that would be displayed should server A be down. This page would live on server B.
I'd also like a similar thing so that if server B is down the domain resolves to server A and a holding page is displayed.
I guess I'd have to make an user account for each domain on each server and put the 'Unavailable' page on the secondary server - what I'm not sure about is the order in which the domain resolves and how to control this.

I don't want to mirror the whole site - just avoid having the situation where the domain doesn't resolve and the client gets a 404 error.

Hopefully some of that makes sense! Is this possible and if so what would I need to do to configure it? Am I making this complicated or is there a simple way to do this I have overlooked?

Thanks,

inky

[AndrewT]

That is really a very difficult process to do. It would require a complete DNS solution that has failover options, for the life of me I cannot even remember the name of the company that offers this, if I think of it I'll post it up here. Someone else might know as well.

[CasualObserver]

http://www.zoneedit.com/ is the one I believe you are trying to remember.

[george]

I don't think DNS would work in that way. Your clients' domains could only one primary name server active in fact, thus it's possible when your domains settings pointing with ns1.mydomain.com ns3.mydomain.com, they could be shifted to another server when primary name server not available (and once it happen, it wouldn't turn back maybe). And there still has domain-cached delay-time for a long time.

I suggest that you needn't think about the issues server A or B down, in most case they wouldn't down, and almost no DNS solution could make that changes taking effect immediately.

[Grunfeld]

Maybe try www.easydns.com, they are pretty good and fast with dns change issues .....

[george]

Just AS IF fast, local domain cache cannot be overcome.

[Amitabh]

I am not sure if I am getting it correctly right now, but I have seen a load balancer/failover device working prefectly well.

What happens in this case is that the dns of the somain resolves to the device, not to the actual server. The device then decides which actual server is to be used for serving content. This way failure of one server does not affect other servers, although s single point of failure still exists in the form of the load balancer/failover device.

Another method I have seen is to have servers at multiple locations, each location a mirror copy of the master server. There has to be mutiple DNS entries in this case. From what I presume in this case, if the browser fails to reach the domain wit the first IP, it will try the next IP in the DNS answer (not sure about this though).

The third and most expensive way to go is through various Content Delivery Networks (CDN) like Akamai, globix, limelight, mirror image, navisite and maybe a few others. They have their own delivery systmes already in place, so one single point of failure genreally doesn't affects the website.