I’m working with a customer at the moment who has a few problems with their Exchange Server environment.  Most of the problems stem from explosive growth in staff numbers without all of the right standards and procedures in place to ensure that the Exchange system would scale upwards and continue delivering the required KPIs.

One of the problems is an unbalanced distribution of mailboxes across the various mailbox databases on the Exchange servers.  The reason for this is quite simple – each of the mailbox databases is given a name along a standard, but this name gives no indication as to which mailboxes should be placed on it.  In fact there is no system in place to determine where a given mailbox should reside.

As a result of this whenever a new mailbox is created it is placed at random onto one of the mailbox databases.  After a few years of this practice we can see that some databases have just a few dozen mailboxes in them, whereas others have thousands of mailboxes in them.

Unbalanced Database Problems

An unbalanced distribution of mailboxes such as this can cause some serious problems, such as:

• Excessive I/O load on some databases and their back-end storage
• Databases well in excess of recommended maximum sizes
• Long backup and recovery times for the larger databases
• Long maintenance times on the larger databases

A more efficient database layout needs to be designed and implemented to resolve these issues.

Design Considerations

Designing a database layout for an Exchange system takes some careful planning and consideration of the characteristics of the business and network environments.  There is no ‘one size fits all’ approach to this.  As I discussed the matter with my colleagues, these are some of the factors we took into consideration:

• Geographical location of the mailbox servers
• Limitations of the Exchange Server product version in terms of maximum allowed databases
• Mailbox storage quotas, for example VIPs have 2Gb limits but staff have 500Mb limits
• Current size and likely growth of the business in terms of staff numbers
• Maximum recommended database sizes from Microsoft
• Maximum practical database sizes to achieve backup and recovery timeframes
• Naming convention that makes it simple for IT admins to select a mailbox database for new mailboxes

The first consideration is an easy one.  It goes without saying that if mailbox servers are dispersed among the major geographical locations of the business then mailboxes should be placed on the closest server to the user.  So for example, North America users will be placed on server located on that continent, and the database naming convention will include an indicator such as “NAM” or “NAM-East”. Continue reading Designing an Exchange Server Database Layout