I would like to enable mailbox auditing for all of the mailboxes in my Exchange 2010 environment, including Owner actions of SoftDelete, HardDelete and MoveToDeletedItems. From what I've read in Microsoft's sizing documentation they recommend an additional 5-7% of IOPS for mailboxes with auditing enabled.
Has anyone else done this? What has been your experience with enabling it? Any gotchas?
Based on advice that I've received, you should allocate .1-.5 IOPS per mailbox depending on factors such as the number of and type of devices in use. If you're including BES, plan on 1 IOPS per mailbox. If you have 500 mailboxes, at a conservative .5 IOPS per mailbox, you need 250 IOPS to handle your storage load. Adding 7% to 250 IOPS takes you to a whopping 268 IOPS. Sounds pretty negligible in even the most limited disk arrays.
Here is some more information you can use to help calculate your I/O profile for your users: http://technet.microsoft.com/en-us/library/ee832791.aspx