Thank you for your HQ post! I will certainly get back to it if I ever need to do that kind of math.

we just did an eval for EV and Exchange 2010 archving with the following requirements:

10000 users –
a) 1 GB mailbox data (average) in Ex 2003
b) 2 GB (average) in PST files.
c) 2 Gb Growth in 2 years (1 GB mailbox growth is assumed to per user per year)

–> 5GB per user total mail data

They planned to go to Exchange 2010 with a 2 GB mailbox and a personal archive for the rest, or use Enterprise Vault wit a 1 GB mailbox as they can use EV Offline Cache for their mobile users.

The design is using 2 DAGs and another time-lag DAG for providing additional DR options (only for mailboxes, not PAs).

Here is the storage summary we did:

With Exchange 2010 Personal Archives (PAs)

Exchange 2GB/user * 10.000 users * 3 DAGs –> 60 TB Exchange Primary Storage (SAS)
Exchange Personal Archive 3GB/user * 2 DAGs –> 60 TB Exchange Secondary Storage (S-ATA)
Exchange Indexing (15%) for Mailboxes –> 9 TB Index Storage (SAS)

—> All in all we need 130 TBs of Storage for the Exchange environment

Note that there is no SIS in Exchange 2010, so the Mailbox data from 2003 will likely expand and the 1GB growth they assumed from Exchange 2003 might be even larger.

Now with EV:

Exchange 1 GB/user * 10.000 users * 3 DAGs —> 30 TB Exchange (SAS)
Exchange Indexing (15%) for Mailboxes –> 4,5 TB Index Storage (SAS)

2 GB PST in Enterprise Vault * 10000 users * 60% Compression (SIS & Compression) –> 8TB
2 GB Growth for future * 10.000 users * 40% compression (SIS & ZIP Compression) –> 12 TB
15% EV Indexing (on 20TB above) –> 3TB

–> So with EV you need 35 TB for Exchange and 23 TB for EV.

The saving with EV was 70 TB of storage and that paid multiple times the Symantec licenses.
Over the cause of 4-5 years will become even bigger.

Hope this gives another perspective on the cost side….

Daniel Maiworm
GlassHouse Technologies