Maximum Mailbox Stores

While reviewing some information, I came across an interesting fact.  While you can have up to 50 Storage Groups on a single Exchange Server 2007 Enterprise Edition box, you can still only have 50 databases total.

Some background info:  Storage Groups (SG's) are logical collections of databases in Exchange Server.  Information Stores (more often simply "Stores") are the databases themselves.  Each SG has a set of logs associated with it that cover all Stores within the group, and there can be both Public Folder Stores and Mailbox Stores within the same group.

If you intend to use any of the built-in data-replication solutions in Exchange 2007 (CCR, SCR, LCR), then you can only have one Store per Storage Group, which means you can only have 50 stores no matter what.  But if you were planning on not using these tools, and wanted to have multiple Stores per group, then that 50 store limit becomes very important to keep in mind.

Let's say that you have a very large Exchange 2007 user base, and you want to split the users into 25 SG's.  That would mean a maximum of 2 Stores per group.  Even though a SG can hold up to 5 Stores, if you tried to put 5 Stores in each of the 25 SG's, you would exceed the overall server limit of 50 Stores for the box.

Granted, this will most likely not impact the majority of users, but for Enterprise Exchange 2007 shops - and especially Exchange Hosting Services Providers - this is definitely something to be aware of.  Assigning each client or business unit their own Store could quickly fill up the number of Stores available on the server, even if you are nowhere near the total number of SG's allowed.