So I'm prepping our business case for upgrading our Exchange 2007 environment to Exchange 2010 next year (it'll probably be a 2013 upgrade, but the tool doesn't support that yet), and I'm trying to figure out if I missed something in my calculations. Here's my inputs: Exchange Environment Configuration Value Global Catalog Server Architecture 64-bit Server Multi-Role Configuration (MBX+CAS+HT) No Server Role Virtualization No High Availability Deployment Yes Number of Mailbox Servers Hosting Active Mailboxes / DAG (Primary Datacenter) 10 Number of Database Availability Groups 1 Site Resilience Configuration Value Site Resilient Deployment Yes Site Resilience User Distribution Model Active/Passive Site Resilience Recovery Point Objective (Hours) 24 Activation Block Secondary Datacenter Mailbox Servers Yes Dedicated Disaster Recovery Mailbox Servers in Secondary Datacenter No Mailbox Database Copy Configuration Value Total Number of HA Database Copy Instances (Includes Active Copy) within DAG 3 Total Number of Lagged Database Copy Instances within DAG 0 Number of HA Database Copy Instances Deployed in Secondary Datacenter 1 Number of Lagged Database Copy Instances in Secondary Datacenter 0 Exchange Data Configuration Value Data Overhead Factor 20% Mailbox Moves / Week Percentage 1% Dedicated Maintenance / Restore LUN? No LUN Free Space Percentage 10% Log Shipping Network Compression Enabled Log Shipping Compression Percentage 30% Total Number of Tier-1 User Mailboxes / Environment 4500 Projected Mailbox Number Growth Percentage 10% Total Send/Receive Capability / Mailbox / Day 50 messages Average Message Size (KB) 180 Mailbox Size Limit (MB) 10240 Personal Archive Mailbox Size Limit (MB) 0 Deleted Item Retention Window (Days) 14 Single Item Recovery Enabled Calendar Version Storage Enabled IOPS Multiplication Factor 1.00 Megacycles Multiplication Factor 1.00 Desktop Search Engines Enabled (for Online Mode Clients) No Predict IOPS Value? Yes Tier-1 User IOPS / mailbox 0.00 Tier-1 Database Read:Write Ratio 3:2 When I pump everything into the calculator tool, I get about 190TB of email including DBs, logs and overhead in the LUN Requirements tab, but the Storage Design tab wants 680TB of disk in the Primary DC and 340TB of disk in the Secondary DC (all RAID10) for a total of 1PB of storage to cover 50TB of usable email space (if everyone in the company was at their 10GB limit. Does that seem right? Am I missing something in replication or other overhead factors?

Thanks Ed; no, corporate mandate is that everyone gets the same mailbox size (we don't have any good chargeback models to get more granular). We standardize on Dell hardware, so my thought for 10 mail servers was to use their PE720xd as a storage/compute block to deliver the cheapest upfront solution, and they can do about 24TB of raw storage per box. So I was figuring on 10 in the DAG in the primary DC, and 5 in the DR DC (not lagged, but with no active mailboxes). And yeah, I figured around 200TB of total storage for the DAG so I was surprised to see the calulcator spit out 1PB. I'll probably go back and just configure a 3 server DAG with SAN gear behind each so I can get the drive numbers up enough and get a number closer to what my "back of the napkin" calculations came up with...

One thing to consider is that even though you give everyone the same quota, they don't all use it all, so desigining for worst case will leave a lot of space unused. Further, with Exchange 2010, you can probably use large, cheap SAS or SATA drives.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."