I frequently receive the question from our clients as to what the predicted IOPS should be for a Blackberry user when this user will have a mailbox on Exchange 2007. This article is not written in judgment of which mobile email devices are better. Ideally clients will pick a Exchange 2007 centric solution using Exchange Activesync . However we know that many of our clients still prefer Blackberry's and as such we will continue to need to support these and calculate for their use. Thus it frequently becomes necessary to plan how these mobile users will affect the performance of the Exchange 2007 mailbox servers. The general accepted Input Output Operations per second (IOPS) for each Blackberry user is 3.64 additional IOPS per user as recommended in the reference "What Causes Exchange Disk I/O" . You should also reference "BlackBerry Enterprise Software v4.0 for Microsoft Exchange". The recommended IOPS for these users is frequently debated, but per Microsoft and RIM documentation 3.64 IOPS is the generally accepted measurement, which is something I will leave to others to debate.
So what formula should I use to calculate the overall IOPS per user when only some users will have Blackberry's . This formula could be expressed as follows.
("#of Exchange Mailbox Users" * "IOPS Profile / Mailbox") + ("# of Blackberry Users" * 3.64) = Total IOPs
Thus a single blackberry user with 0.48 IOPS in cached mode could be calculated as
(1*0.48) + (1*3.64) = 4.12 IOPS for one user
1000 users with 0.48 IOPS / user with 500 of these users using a Blackberry could be predicted as such
(1000*0.48) + (500*3.64) = (480) + (1820) = 2300 Total IOPs for all users
So what is an easy way to place these calculations into the Microsoft Exchange 2007 mailbox Server role Storage Requirements Calculator found on the Microsoft Exchange Team Blog?
I recommend the following.
First determine your total number of Blackberry users. Let's assume 500. Now take your 500 users and multiple by 3.64.
500 * 3.64 = 1820
Place these IOPS in the "Additional I/O Requirement / Server" found on the Input Tab under IOPS Configuration of the Microsoft Exchange 2007 mailbox Server role Storage Requirements Calculator.
As such for a single mailbox server, LCR server, CCR or SCC cluster you would enter in the full 1820 IOPS into the Additional I/O Requirement / Server.
What if I wish to distribute my Exchange mailboxes and these Blackberry users over multiple mailbox servers, LCR servers, CCR or SCC clusters? Then you would divide the 1820 by the Number of Exchange Mailbox Servers you entered. In this example I entered 2 CCR clusters. Therefore I divided the 1820 additional IOPS needed by 2 and entered 910 IOPS in the Additional I/O Requirement / Server.
Forrest McDuffie
Senior Consultant
Project Leadership Associates
