Exchange Server 2007 Recommended Maximum Mailbox Store Size

The other day I had a customer ask what the recommended maximum database size is for Exchange Server 2007 mailbox stores.  I knew I had seen the information somewhere on-line, so I did some Googling.  Initially, I didn’t have much luck. 

First of all I found the article below, which recommends stores grow no larger than 50GB. On the other hand it also mentions .stm files (no longer used in Exchange 2007), so I wasn’t convinced it is still relevant.

http://technet.microsoft.com/en-us/library/aa995715.aspx

Then I found KB823144, which also recommends a 50GB max, but the article only applies to Exchange 2003.

After that, I found the following Blog entry written by Gerod Serafin.  The article references some Microsoft on-line content that talks about different recommendations, but comes back to the 50GB recommendation.

http://blogs.technet.com/gerod_serafin/archive/2007/06/11/200-gb-limit-on-database-sizes.aspx

Feeling somewhat confused, I put the question to the Exchange MVP brains trust.  I was referred to the on-line Technet article that covers Mailbox Server Storage Design.  This provides the authoritative recommendation for Exchange Server 2007, as quoted below.

We recommend the following maximum database sizes for Exchange 2007:

• Databases hosted on a Mailbox server without continuous replication: 100 GB
• Databases hosted on a Mailbox server with continuous replication and gigabit Ethernet: 200 GB

  Note:

  Large databases may also require newer storage technology for increased bandwidth to accommodate repair scenarios.

  Important:

  The true maximum size for your databases should be dictated by the SLA in place at your organization. Determining the largest size database that can be backed up and restored within the period specified in your organization’s SLA is how you determine the maximum size for your databases.

For me, the key element is the comment regarding the SLA in place within your organisation.  When carrying out a high level design the 100GB/200GB recommended maximums shown above are good starting points, but these may need to be adjusted during your proof of concept phase.