Friday, 6 February 2015

Exchange 2013 - storage space capacity calculator

Here is a nice and quick calculator for a basic estimation of the space capacity required for Exchange databases and logs. It's based on the formulas and recommendations presented by Jeff Mealiffe in Ask the Perf Guy: Sizing Exchange 2013 Deployments.

How to collect the required input data and how it's all calculated is explained here.

The formula for Transport DB size ends with "x 2 copies for high availability". The part in front of it calculates the size of the DB processing active DBs (X), and then this HA part multiplies X with 2 passive copies that protect the system from double server failure. So they multiply the X with 2 HA copies and double it (2X). But if there was only 1 active set of DBs (no DAGs) or 1 copy (A/A or A/P), then X would not change for either 0 HA copies or 1 HA copy. I'm not sure how it doubles with 2 HA copies.

I guess we should calculate the TDB size for active DBs and see what happens after HA copies are added.

Overall Daily Messages Traffic = number of users x message profile

Overall Transport DB Size = average message size x overall daily message traffic x (1 + (percentage of messages queued x maximum queue days) + Safety Net hold days) x 2 copies for high availability

Ask the Perf Guy: Sizing Exchange 2013 Deployments

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