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  1. #1
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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?

  2. #2
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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...
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  3. #3
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    Quote Originally Posted by SLDHosting View Post
    Yes this is possible I believe.

    Why not just get a cheap VPS from a budget provider for NS3?
    Eventually I will do this, I only want to pay for 2 vps right now though.

  4. #4
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    Quote Originally Posted by Zach Nelson View Post
    Eventually I will do this, I only want to pay for 2 vps right now though.
    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 have
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  5. #5
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    Quote Originally Posted by SLDHosting View Post
    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 have
    Seems logical, I'll just go with 2 nameservers then.

    Thanks

  6. #6
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    Quote Originally Posted by Zach Nelson View Post
    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?
    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.
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  7. #7
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    Quote Originally Posted by hhw View Post
    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.
    How does normal DNS work? Doesnt the request go to the first record on a domain, and if it fails it goes to #2 and so on?

  8. #8
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    Quote Originally Posted by hhw View Post
    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.
    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 anyway
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  9. #9
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    Quote Originally Posted by hhw View Post
    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.
    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...

    Quote Originally Posted by Zach Nelson View Post
    How does normal DNS work? Doesnt the request go to the first record on a domain, and if it fails it goes to #2 and so on?
    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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  10. #10
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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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  11. #11
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    Quote Originally Posted by aodat2 View Post
    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.
    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

  12. #12
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    Quote Originally Posted by F-DNS View Post
    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
    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 ?

    Quote Originally Posted by timpane View Post
    I desire to have a dedicated server and two virtual personal servers. I design on utilizing the dedicated server for the world broad web server and the virtual personal servers for DNS.
    cPanel/WHM + cPanel DNS ONLY does this wonderfully
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  13. #13
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    @SLDHosting - I should probably have put "like proximity of DNS resolvers to root servers"

    Quote Originally Posted by SLDHosting View Post
    You know what, You just got me hooked on that bit of information and am eager to know more
    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)

    Quote Originally Posted by SLDHosting View Post
    Would you mind starting another thread with more information about it because I think it would make a very interesting read ?
    What, the bit you quoted or all of it? Sheeesh! You'll have me typing for a week!

  14. #14
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    Quote Originally Posted by F-DNS View Post
    What, the bit you quoted or all of it? Sheeesh! You'll have me typing for a week!
    All of it, No rush, I just think it would make a VERY good read and the community would benefit from it aswell
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