Multi-master (HA)

[Marty Lee]

Josh,

we use multiple masters across multiple hosts, with mysql as a backend for the zone data.
Each DNS server is a master and has it’s own local mysql DB.
Each mysql database is then kept in ‘sync’ using mysql replication over a VPN link from a single
(private) admin host.

The single admin host (i.e. master mysql database) sits on a cluster framework, so it
is HA.

By doing things this way, if we do have any problems with our primary admin cluster, all
the other DNS servers continue to serve clients without interruption. If there is a big
problem with the admin cluster, it doesn’t take long to repoint the replication to another
system or even just run manual mysql updates on the databases, if it really came down to it.

From my experience, systems often need to resolve hosts to boot cleanly (ntp springs to mind),
so having the DNS daemon itself in a cluster/HA control, often means it will only be started once
the main OS has started, which is often a wee bit too late.

Hope this is of some use… If you do go down the ‘putting named under cluster control’ route, just
check that your local host doesn’t need it before cluster starts it up :-) I’ve seen that bite a
number of my customers before...

cheers

marty


On 6 May 2014, at 19:20, Baird, Josh <jbaird at follett.com> wrote:

> Hi,
> 
> For those of you who operate at multiple sites or datacenters, are you doing any HA for your BIND masters?  Ideally, we would have a master in each datacenter; maybe not an active one, but one that is standing by in case your primary master becomes unavailable.  
> 
> Do you have multiple "active" masters and list them as master in each of your slave's zone definitions?  This seems like it could get rather messy.  One thought is to use a technology like VMWare SRM which will spin up a master/virtual machine automatically in a second datacenter if your primary master goes down.  This coupled with Layer2 connectivity between your sites could make things fairly simple.  The standby/secondary master would retain the same IP address as your primary, so everything should just *work*.  
> 
> What are others doing?  Any thoughts, ideas or advice is much appreciated.
> 
> Thanks,
> 
> Josh
> 
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-----
Marty Lee                         e: marty at maui-systems.co.uk
Technical Director                v: +44 845 869 2661
Maui Systems Ltd                  f: +44 871 433 8922
Scotland, UK                      w: http://www.maui-systems.co.uk

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