How to Calculate Exchange Server Disk System Requirements
Exchange server disk system plays a major roll in large Exchange environments because it is heavily affect the performance.
Only having performing servers can’t achieve required performance. Microsoft always recommend to have disk usage counter
below 0.80 to meet user performance requirement.
Disk usage counter can be calculated by IOPS per mailbox multiply by number of users and then divide it by Total IOPS/sec.
Disk Usage = ((number of users) × (current IOPS per mailbox)) ÷ (total IOPS/sec)