I'm migrating an Exchange 2003 environment to Exchange 2010. The hardware has already been spec'd and is in place for our 2010 requirements but the back up solution is going to be upgraded separately. With that in mind I need to workout the likely storage uplift in changing from 2003 to 2010. Our current backup solution is spec'd for Exchange 2003 and has limited capacity for expansion.
We will not be increasing mailbox sizes until the new backup solution is in place but Exchange 2010 storage model changes means there will be an increase in data size regardless. I basically need to know what my current Exchange 2003 database sizes will look like in Exchange 2010. Can anyone advise how I can calculate or estimate this (e.g. combine .edb and .stm file sizes and add 5% for CI)? I've search the web but I can't find a clearer answer than between 20% - 50%.
Thanks
