Tuesday, 11 March 2008

64bit Domain Controllers

What's the benefit you may ask, well plenty if configured correctly!

Here at Cobweb we've just finished our deployment of 64bit DC's. The project was started as we realised if we kept our existing 32bit Domain Controllers we would actually have to double the number to support both our existing Exchange 2003 infrastructure and the soon to be deployed Exchange 2007 service we are launching. Supporting 40,000 mailboxes (approx: at this time) takes a lot of Directory work and the last thing we wanted to do was rack and deploy another farm of Active Directory servers - especially when Rack Consolidation is proving to be so important now with power restrictions DataCentres are starting to enforce.

Ultimately we were left with only one option, upgrade to 64bit.

The general rule of thumb for 32bit GCs is to have 1 processor core for every 4 Exchange processors cores. Note I mention core - not actual processor. Having a 64bit GC extends this support to 1 core for every 8 Exchange cores - as long as the server has enough RAM to support loading the entire of the directory (NTDS.dit file) into RAM.

Thus upgrading to 64bit Directory servers allowed us to keep the same physical number of servers, without having to worry about rackspace or power considerations - and indeed cooling - and has given us the support for both Exchange 2003 and Exchange 2007 into our infrastructure.

Oliver Moazzezi

MVP - Exchange Server

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