TPOV

Ever since the first betas of Exchange 2010, one of the most discussed features is the Database Availability Group; DAG. Without going into all the details of DAG, it truely is huge step forward in Exchange High-Availablility, primairily because it’s so very, very easy to configure.

Exchange 2010 comes, just like previous versions, in two flavours; Standard and Enterprise. There is just one single product, but the serial key you enter will determine the version. As long as you are running in trial mode, the installation is an ‘Enterprise’ version. Although the pricing is not yet available, traditionally the Enterprise Edition is about 4 times the price of the Standard Edition.

First thing we see is that the Standard Edition is limited to 5 databases per server. The Enterprise Edition scales up to 100 databases per server. Based on the beta documentation, it looks like DAG is available in the Standard and in the Enterprise Edition.

But you have to remember that DAG requires some Windows clustering components, only available in Windows Server 2008 Enterprise Edition. (And this edition again is about 4 times the price of the Standard Edition.)

So before getting all excited about DAG, please check if you company is willing to go with at least 2 Windows Enterprise Edition servers…

So is there an alternative to DAG?
In Exchange 2007 we had a whole bunch of stuff available for high availability and redundancy. SCR, CCR and even LCR. DAG looks a little like a mix-and-match of all these technologies. Hence, the old ones are gone from Exchange 2010. So besides DAG there’s really nothing left.

Looks like if you take your Exchange installation seriously, you will have to get ready to purchase some Windows Enterprise Licenses… Sorry about that…