How to configure storage groups in Exchange Server 2003

This article outlines the storage group configuration that we currently recommend for computers that are running the Enterprise Edition of Microsoft Exchange Server 2003 or that are running Microsoft Exchange 2000 Enterprise Server.

In versions of Exchange that are earlier than Exchange 2003, we generally recommended that you fill a storage group with five databases before you create an additional storage group.

However, starting with Exchange 2003, the recommended database and storage group configuration has changed. When you use Exchange 2003 or a later version of Exchange, we now recommend that you add an additional storage group for each new database until the maximum number of storage groups has been created. We recommend that you do this instead of adding multiple databases within a single storage group.

The reason for this new recommendation is that virtual memory management improvements were made in Microsoft Exchange 2000 Server Service Pack 3 (SP3) and in later versions of Exchange.

This new recommendation lets administrators spread the load of mailboxes across as many stores and storage groups as possible. This creates a more easily manageable Exchange storage topology. Such a topology has the following advantages:

• Databases can be smaller.
• Drive input/output (IO) can be better managed.
• Recoverability increases.

For example, consider the following configurations for Exchange storage topology. In these examples, the storage groups are named SG1 through SG4. The databases that are created over time are named DB1 through DB8.

In versions of Exchange that are earlier than Exchange 2003, you may have configured your Exchange storage topology as follows:In Exchange 2003 and in later versions of Exchange, we now recommend that you configure your Exchange storage topology as follows:

In versions of Exchange that are earlier than Exchange 2000 Service Pack 3 (SP3), each storage group pre-allocated approximately 250 megabytes (MB) for the version store, the schema cache, and other JET resources. Therefore, virtual memory allocation was quickly consumed.

Starting with Exchange 2003, memory allocation has been made even more dynamic. This dynamic memory allocation removes the pressure on memory.

Databases in a storage group are not fully independent because they share transaction log files. As the number of databases in a storage group increases, more transaction log files are created during regular operation. The larger number of transaction log files requires additional time for transaction log replay during recovery procedures. The longer time for transaction log replay leads to longer recovery times.

When you maximize the number of storage groups on a server, you can take advantage of separating log traffic. Additionally, data recoverability is improved.