Dreamhost has actually been pretty decent over the past year, but this month there have already been a number of unplanned issues that have brought down the entire site and email server.

Previously I'd been thinking about changing hosts, but no matter who I looked at, I also found plenty of horror stories. Including with Media Temple. So now instead of "moving" the site I'd like to copy and mirror it.

But I have no idea how to do this nor what's involved. The idea would be to create a fault tolerant setup such that if one server goes down the other one can pick up the slack.

Is this even possible using two different shared hosts? Possible with two virtual private servers? Some kind of gateway/balancing system in the middle? What if that fails?

Any recommendations and advice greatly appreciated. It's already important now because it accounts for lost sales. It will become much more important as I try to expand the business.

Thanks to the way DNS works it isn't really possible, or at least not unless you have some third hosting solution that you can absolutely rely on to be up all the time. At which point you'd just be better off hosting on the reliable hosting solution in the first place...

Damn you DNS! Yeah, I'd really need a way to resolve two unique paths, letting one fall back to the other.

Actually, you sorta can do it.

Host your DNS server on the same server as the web server. Instead of having identical copies of the zone, have each DNS server resolve the web address to its local web server. Also set the DNS record in question to have a small TTL.

If one web server goes down, the DNS goes down along with it, and the remote system will only be able to resolve the one that's still up.

The only people affected will be those using the site when it goes down, and then only for as long as the TTL, at most. That said, some ISPs will ignore DNS TTLs and hold onto DNS records as long as they feel like. The only one I knew of for sure was AOL, and they're pretty much a non-player now. I don't know if anyone's currently doing it or not.

You will have to build some logic into your web app so that either the backend data is shared or to make the client always hit the same server. Or, instead of having two web apps running simultaneously, have one check the status of the other somehow and redirect to it if it's up or take the session if it's down.

Also, if no one's ever done this before (doubtful), I claim prior art!

What about a constant backup of one site to the other, and when DreamHost goes tango uniform, repoint the DNS records by hand?

Sure this isn't a 100-percent uptime situation, but would it be better uptime than not doing it at all?

Maybe it is different in US ISPs, but I've seen UK ISPs hang on to DNS entries for days when the TTL is set to a couple of hours.