EDIT: This post has been updated on 5/24/2013 for the new version of calculator. For the list of latest major changes, please see THIS.
Overview
The Exchange Mailbox Server role is arguably o...
Updated Apr 22, 2020
Version 4.0
Blog Post
AG - In Exchange 2010 due to the store schema changes and the ESE changes, our IO profile is vastly different. As a result of that Outlook Online Mode and Outlook Cached Mode behave the same from an IO perspective.
Where a difference comes into play is the use of desktop search engines. If you are deploying a desktop search engine with your online mode clients, there could be additional read IO overhead (similar formula to what was used in the Exchange 2007 calculator for online mode clients). The only desktop engine that doesn't have this effect is Windows Desktop Search 4.0 (and later) as WDS4.0 uses ICS to do the crawling of the mailbox (and thus behaves like cached mode).
Where a difference comes into play is the use of desktop search engines. If you are deploying a desktop search engine with your online mode clients, there could be additional read IO overhead (similar formula to what was used in the Exchange 2007 calculator for online mode clients). The only desktop engine that doesn't have this effect is Windows Desktop Search 4.0 (and later) as WDS4.0 uses ICS to do the crawling of the mailbox (and thus behaves like cached mode).