Wednesday, 11 June 2014

DNS are a DBA's best friend

Pah who needs diamonds.  A few DNS address can make you life much more simple.

SQL 2012 + Method 

In SQL 2012 high availability groups Microsoft brought in the ability to use a single Arecord.  This means that you can choose a set of databases that are related to a single product and have them six in a box with a virtual server name, that can fail over to DR with them.  an example set up below.

SERVER1 - Primary sever

DRSERVER2 - Your DR server

You could  have all databases related to say communications sitting in an AG.


These would all now have a virtual server name of say SQLComms

So no matter what server your databases now end up on, any application pointing to the arecord of SQLComms will see the right server.

All very useful as you can ensure that you have seamless DR, and also allows you to move databases about with ease.

NOTE You will still need to ensure that correct users sit on both servers.

 Pre SQL 2012 Method

The same can be achieved in older versions of SQL, however it does require a bit of manual intervention.

Set up a Cname (alias) for the same set of databases, you can then re-point this name to the failed over DR server once your at DR.

Another good use for this, is to stop hard coded server names.  If as far as every one else is concerned the server name is that alias, you can always just pick up and move the databases.

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