My company's been hosting web sites for about a year now. Since then, and up until now.. I've been looking for ways to co-locate a backup site (mirror) of these sites.. however, since I'm using Windows 2000 Server IIS 5.0, I wasn't able to do such.
My question is, how could I make a secondary point of access to the sites say, if my primary webserver located at my primary site goes down. Since each domain has a unique ip... how could I assign another ip address (i believe this is called round robin dns however, it's not proven accurate coz the dns will only throw the address of the last failed ip).
Please, i'm in desperate need of any inputs. The idea is for me to host sites in a 24x7 system meaning i don't have any room for failures.. even for a minimal downtime...
I read somewhere that this could be done if both servers were nameservers too.
If you set a very low TTL for the domains, that would force a lookup of the IP often. You can then make NS2 a copy of NS1, as far as web sites are concerned. Sites would be hosted on these 2 servers.
But instead of creating a master zone and a slave one, use 2 masters where the IP for the site is different, pointing to itself.
So, as long as both NS are working, people end up with one IP or the other for the sites. If one should stop working, people would end up looking in the others' database, which would give them its address and still serve the sites.
- prime [[email protected]]
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what prime says is correct with one caveat. Make the second box a secondary server, not a primary. Then go edit the zone manually without changing the serial number. This works beautifully and is the theory behind a number of load balancers and "up-time gaurantee" devices.
Here are some other solutions :
a) Buy two copies of W2K Advanced Server (~ $3000 a copy) and use network load balancing.
b) Buy two copies of W2K Advanced Server (~ $3000 a copy) and some additional hardware to run cluster service.
c) Run an RFC-compliant DNS server in round robin.
d) Buy a hardware solution. There are tons.
The problem with (a) is it's expensive and NLB is not very effective. The load balancing is actually not too bad, but in the event of a service failure (e.g. IIS) but the box is still up, NLB does NOT kick in.
As for (b): it is VERY expensive.
c) It's cheap but if one box goes down, you will have a 50% failure rate (assuming you have 2 boxes) of users hitting a site. (Better than 100% I guess.
d) This option is pretty darn good for up-time, but the price makes it only viable (not talking about eBay pricing. . .) if you need your site balanced over 3 servers.
As for us? We are a software development company, so we wrote an application by which our dns servers perform snmp health checks against the servers and changes what IP is handed out on each query. This helps to make it as fast as possible with as little cash outlay as possible and maximizes uptime. In the last three years or so, we haven't had down-time even with hardware failure - so something seems to be working . <Knocking on wood>
If you can develop your own solution, it often is cheaper than these tools out there. If you can't, try some of these hardware solutions off of the auction sites. Some are excellent.
Without knowing your budget and some requirements, I can't make a very good recommendation.