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Exchange 2013 Databases - How many?

tparrett asked
I'm in a network where we're running an Exchange 2010 box with 50 users.  We're looking at acquiring a company of  800 employees and will be installing a new Exchange system for all 850 users.  I'm just now starting to plan and prepare.  Wondering if someone can give me a "general" answer of how many databases I should consider making.  So far, I've found in researching answers that are for MUCH larger installations and I'm nervous about going from a very small exchange environment to a much larger one.  All of the mailboxes are for general office workers that average about 100 emails per day.  Maybe half of the users only have about 50 emails per day.  Anyone willing to share their experience?
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Senior Solution Architect
Most Valuable Expert 2015
Top Expert 2015
I would recommend looking at the below Exchange 2013 cheat sheet for database sizing requirements.

The link above also goes over the number of processor's RAM etc based on your requirement. It also outlines virtualized environment as well.

Another important thing to consider is how big are the current mailboxes that you are inheriting? Mailbox databases should be around 150-300GB to ensure that you can do maintenance and or recovery for mailboxes (if needed).

This also plays into the backup procedure as well. The larger the database is, the longer it will take to do maintenance or perform a backup and/or restore.

You will need to see what verion of Exchange server you will be using. Exchange Standard is only allowed to have 5 databases per server. Where Enterprise can now have 100.

Databases can in fact be much larger than i had mentioned above theoretically (16TB) but this is not practical.

Also take a look at the specific storage options for Exchange at the link below.