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Question for Tristan

Discussion in 'General Discussion' started by nibb, Dec 7, 2012.

  1. nibb

    nibb Well-Known Member

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    You cannot posts in older topics so I created a new one. I would like Tristan to chip in as I read he suggested most of the DNS configurations in topics.

    My question is related to 4 cPanel DNS only servers like here:
    http://forums.cpanel.net/f5/dns-cluster-best-practices-large-scale-servers-146757.html

    Where Tristan commented.

    I think his question was rather is he had to configure in WHM in the basic settings all 4 DNS nameserver, not in the DNS cluster, but in the WHM initial setup.

    My guess is yes correct? So all future servers would use the same DNS names.

    What exactly is the benefit of running 4 vs 2 cPanel DNS only in this setup? Load? Each one processing 25% requests in instead of 50% hitting each one? Yes or not? Because as far as I know, DNS in a domain would resolve randomly, not in any particular order.

    I also read forums and tutorials of people guiding on cPanel DNS only to put them on different countries because that would add a speed latency benefit. Example, DNS only in Europe would serve European requests and US cPanel DNS Only would serve US requests. As far as I know this is completely not true with BIND and cPanel DNS only. So this information is widely spread wrong.

    A user in europe could just hit as well the cpanel DNS Only server in the US and he would not be benefit from the speed latency increase of having another DNS server closer to him. Maybe you can confirm this Tristan but as far as I know the names ns1, ns2, etc are just visual mocks, they don´t serve in any order and requests can go randomly.

    It would be also nice for users, what load do you expect to be reduced with this, like BIND uses allot of RAM and I assume with this 4 DNS setup you can turn BIND off in every cPanel/WHM web server correct? If yes, are this DNS still redundant? Because as your posted configuration DNS servers itself do not talk to each other, they do not sync between them and neither do servers. Even in the cPanel Guide its says not too. So this is a concern I had.

    If we go with comments like this:
    http://serverfault.com/questions/13...iple-secondary-ns-servers-improve-performance

    I see absolutely no point in having 2 vs having 10 DNS servers, as they will not really spread load, mostly it will increase redundancy and 2 are just fine if they are separated. Does having more than 2 in the case of cPanel DNS really reduces load on each cPanel DNS server? Or not?
     
    #1 nibb, Dec 7, 2012
    Last edited: Dec 7, 2012
  2. electric

    electric Well-Known Member

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    I'm not a DNS expert, however I can pitch in a few thoughts:

    1. Having multiple DNS server increases redundancy. If ns1/ns2/ns3 servers are dead, then ns4 might still be alive. The odds of losing THREE nameservers are pretty low.... Personally, we use four nameservers, but in retrospect I think we should have only used three. The odds of TWO of our nameservers dying at the same time are very low.

    2. You can disable BIND on the web server if you are not using it to host DNS. (So only your DNS-Only cpanel servers need to use BIND. You can disable BIND on the webservers to save resources.)

    3. When a browser looks up a domain, the DNS query is normally sent to the local ISP. The local ISP then checks its cached DNS data, and if it is not available, then it looks up the domain's nameservers and randomly picks one. After that, all future DNS requests by the browser are answered by the local ISP's DNS cache, until the TTL (time to live) value expires, when the cycle repeats.

    4. I do not believe DNS queries use geo-location by default. So if you have ns1 in EUROPE and ns2 in USA... I don't think it matters where the customer is located. They (well, their local ISP, as per point #3 above) will simply pick a random nameserver from the domain registration. The idea behind "distributed" DNS servers is mostly to avoid network related problems. For example, if major networks in USA go down, then ns1 in EUROPE might still be working.

    I hope that helps.
     
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