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Thread: DNS Clusting Question
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05-15-2011, 09:31 PM #1Web Hosting Master
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DNS Clusting Question
Hi,
I want to have a dedicated server and two virtual private servers. I plan on using the dedicated server for the web server and the virtual private servers for DNS. I know I can setup the two vps with cPanel DNSOnly, but I also want to setup the web server as NS3 incase of a catastrophic failure with both of the vps. Is this possible?
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05-15-2011, 09:33 PM #2Hello World
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Yes this is possible I believe.
Why not just get a cheap VPS from a budget provider for NS3?
Somewhere like citynethost has a budget vps for like $2 a month...UK Based Proactive Server Management.
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05-15-2011, 09:35 PM #3Web Hosting Master
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05-15-2011, 09:39 PM #4Hello World
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The only problem is with having 3 nameservers is that I have found some domains only take either 2 nameservers or 4 namesevers they wont allow to take an odd number...
If you get 2 VPSes in 2 different locations, 2 different datacenters with 2 different reputable companys, You wont have any major issues unless someone launches an attack on your nameservers which in that case your screwed no matter how many nameservers you haveUK Based Proactive Server Management.
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05-15-2011, 09:43 PM #5Web Hosting Master
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05-15-2011, 09:50 PM #6Web Hosting Master
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To make sure we understand correctly, you want your DNS to usually only go to your two VPS'es, but in case both VPS are down, you want your dedicated server to kick in?
Your requirement to have both VPS fail before the dedicated server kicks in makes this a bit more challenging. You'll either need to use a DNS provider with load balancing capabilities that can handle that kind of logic, or you'll need all 3 servers on the same network segment so that you can use some form of VRRP. If you're going to use a DNS provider, there's not much point in running your own name servers, so let's focus on the latter method.
First, you'll need two virtual IP's, one for ns1 and one for ns2, setup with VRRP with the following priorities.
Virtual IP 1
------------
VPS 1 has highest priority
VPS 2 has second priority
dedicated server has third priority
Virtual IP 2
------------
VPS 2 has highest priority
VPS 1 has second priority
dedicated server has third priority
Honestly though, it'll be much easier just to have all 3 servers working and allow the failover to be handled by the DNS protocol.ASTUTE INTERNET: Advanced, customized, and scalable solutions with AS54527 Premium Performance and Canadian Optimized Network (Level3, Shaw, CogecoPeer1, GTT/Tinet),
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05-15-2011, 09:52 PM #7Web Hosting Master
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05-15-2011, 09:54 PM #8Hello World
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Then things start to get very messy when things go wrong when we start talking load balancing, As we're adding more into the mix to go wrong, etc The key to keep things not messy is to keep them simple.
The chances of having 2 VPSes down at the same time with 2 different providers using 2 different datacenters is pretty slim anywayUK Based Proactive Server Management.
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05-15-2011, 10:43 PM #9Retired Moderator
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Or even, have at least one nameserver and one webserver working at any given time, with failover to point the DNS to the working webserver...
No. All nameservers are equally valid, and any of them may be used to resolve your domains. Failover involves changing the DNS records on all [working] nameservers to point to a working webserver.Chris
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05-15-2011, 10:55 PM #10Web Hosting Master
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Hello OP,
DNS (in the registrar) does not really work the way it looks to be working. The DNS there does not bother which it goes to. It basically is something which I am trying to figure out for quite some time and I'm not able to find out.
Lets say for example you have this setup in your Doamin Name.
DNS1 : ns1.yourdomain.com (1.1.1.1)
DNS2 : ns2.yourdomain.com (2.2.2.2)
DNS3 : ns3.yourdomain.com (3.3.3.3)
DNS4 : ns4.yourdomain.com (4.4.4.4)
It does not mean that the DNS will search DNS1, then DNS2, then DNS3 and so forth. It just randomly picks out whichever DNS and goes with it. So if you're planning on using your DNS (in the domain) as a failover thingy, then I'm sorry but you can't do that. For some people, it might go to 1.1.1.1, then out of the blues, it could change to 3.3.3.3 and maybe even 4.4.4.4. Even if your server at 1.1.1.1 is the fastest, nearest and etc.
If anyone knows how this DNS is picked then could you please explain it to me? I'd like to know as well.Last edited by aodat2; 05-15-2011 at 10:58 PM.
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05-16-2011, 08:34 AM #11
It's not as random as you think
We've been collecting data for some time looking at where DNS requests come from in relation to where we position DNS servers. There doesn't seem to be any simple explanation or formula involved, more that look-up sources tend to 'befriend' certain DNS servers based on geographical location, speed of response, connectivity between the 2 points, etc.
So, just as an example, our DNS in San Jose CA tends to receive more requests from the west coast than east (with exceptions), plenty from China and almost none from Russia. Our DNS in New York and London will receive a much wider spread of requests because of the better connectivity and peering in those locations, whilst Bucharest and Stockholm generally receive requests that are more localised.
That hints towards geographic favouritism but network comes into play too. Some networks appear to query DNS servers closer to them (Verizon, Level3, Telia are examples) whilst others tend to query a single DNS area regardless of their position because they can connect to it easily. Comcast is an example - They tend to favour our west coast servers and we receive occasional requests from Comcast IPs in, for example, Boston MA which completely ignore our servers around NYIIX and anything we have in between, like Chicago or Dallas.
There's other factors that come into play like proximity of DNS servers to root servers (TLD and ccTLD) but I don't want to drift into rant mode and hijack this thread
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05-16-2011, 01:54 PM #12Hello World
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You know what, You just got me hooked on that bit of information and am eager to know more, Would you mind starting another thread with more information about it because I think it would make a very interesting read ?
cPanel/WHM + cPanel DNS ONLY does this wonderfullyUK Based Proactive Server Management.
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05-16-2011, 05:16 PM #13
@SLDHosting - I should probably have put "like proximity of DNS resolvers to root servers"
Be careful or you'll turn into a DNS "anorak" like me LOL. I've been figuring it out (or trying to) since before the Internet was invented - Right back to the days of Fidonet nodelists. (70% of the members here won't know what a Fidonet nodelist was, the other 30% won't admit it 'cos they'll be showing their age)
What, the bit you quoted or all of it? Sheeesh! You'll have me typing for a week!
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05-16-2011, 06:39 PM #14Hello World
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