Originally Posted by mbr
Sorry for the somewhat confusing title. My DNS setup right now is the latter, "single diversified" meaning, I host both the web server and DNS server on the same box per group of clients. For example:
Client Group A
NS1 and NS2 is hosted on the same box with the web server A
Client Group B
NS3 and NS4 is hosted on the same box with the web server B
and so on...
I am thinking of making a "centralized clustered" DNS server so that my setup would become like this:
NS1, NS2, NS3, etc. would be on geo-separated servers all containing the same DNS info and they will host the groups of clients at Server A and Server B, etc.
Now my question is, what are the disadvantages of the two setups? What I can think of right now is "centralized clustered" can be a single point of failure for DDoS attacks while "single diversified" isn't since only one group of clients will be affected in case of an attack. What you think?
Having a DNS cluster and separating the DNS servers is ideal and would reduce the DNS load on the servers. Depending on how many domains you're hosting a perfect setup would be:
1. Have 2 DNS Servers for example dns1 & dns2
2. Setup a cluster among all
3. Set backups of dns1 to store on dns2 and vice versa or use remote NAS for backups.
In this setup the accounts can be migrated to / from any server without the requirement of a DNS change (no downtime). Have backups set as stated in point 3 which would help in the event of any server failures at which point accounts can be restored from backups to another server with less downtime.
The idea of a DNS cluster is regularly considered as being more complex than it really is. In actuality, a multi-server DNS cluster transfers any zones on the given machine to the machines you add to the list. For example, if you have server X and add the IP for server Y to the list, whenever you add a domain on server X, server Y will receive a copy of the DNS zone. Server Y will now be able to resolve the domain. Of course, these are the basic intricacies of how the DNS cluster works but hopefully this helps outline some of the benefits of a DNS cluster.