So I am trying to sketch out some mailbox server scenarios for my Exchange 2010 design. I think I am leaning towards iSCSI or perhaps direct-attached SAS drives, but since I am doing virtualized Exchange servers, I don’t think I can load all the storage I need in to the ESX chassis. That leaves me with iSCSI. I am looking at three models to ‘standardize’ on for the business:
Config 1:
1Gb mailboxes x 1000 mailboxes max = 1Tb database
Config 2:
1Gb mailboxes x 500 mailboxes max = 500Gb database
3Gb mailboxes x 100 mailboxes max = 300Gb database
5Gb mailboxes x 40 mailboxes max = 200Gb database
Total = 1 Tb databases
Config 3:
1Gb mailboxes x 500 mailboxes max = 500Gb database
5Gb mailboxes x 100 mailboxes max = 500Gb database
Total = 1Tb databases
If you were to then populate each server configuration in to a Database Availability Group (DAG) spanning three different data centers, you would require a total of 3Tb for each server – not counting OS and log file space requirements. Remember that the rule of thumb is 240ms roundtrip networking latency between any server in a DAG to another server in the same DAG. Also remember, that while servers in a DAG can span Active Directory sites, they cannot span Active Directory domains.