Planning for Journal Recipient Mailbox Servers
For most enterprises that must comply with regulation, hundreds of thousands of messages will be sent to the journal recipient mailboxes on a daily basis. These messages are then likely forwarded, or downloaded to a third-party storage solution offsite. Therefore, it is highly recommended that you house the journal recipient mailboxes on servers that are separate from the regular user mailboxes. This section discusses how to organize the journaling mailboxes and other standard considerations for server sizing.
Organizing Journal Recipient Mailboxes
When it comes to organizing the journal recipient mailboxes, you must answer the following questions:
How many journal recipient mailboxes are required?
How much storage is required for each journal recipient mailbox?
How should the journal recipient mailboxes be configured on the hard disks?
As with all sizing estimates, test estimates in a lab before you implement solutions in your production environment. To estimate how many journaling mailboxes you will require, look at the load on the mailbox servers. In some organizations, mailbox servers are clustered and run at high resource usage levels (80 percent or more). In other organizations, mailbox servers are run below 30 percent load. If your resource usage levels run high, in a lab setting, add a journal recipient mailbox for every three to five mailbox servers. If your resource usage levels run on the lower end, start with one journaling recipient mailbox for every seven to nine mailbox servers.
From an organizational perspective, it may be easier to manage fewer journal recipient mailboxes if you do not plan to hire a third-party to store and organize the data for you. Generally, however, minimizing the number of journal recipient mailboxes is a good practice for reasons already mentioned in this guide (bandwidth, management, performance).
For storage size, there are a number of factors to consider. The list below discusses these factors, but the biggest factor is how much mail is used in the organization. For a simple place to start testing, assume that for each mailbox database that is journalized, you need two to three times the storage space on the corresponding journal recipient mailbox. However, because the messages in the journal mailboxes are largely "transient," meaning that the messages that reside there are quickly forwarded or downloaded and then deleted, you may be able to run closer to a one-to-one storage ratio with the user mailboxes.
Some factors that will affect the storage requirements and performance characteristics of the journal recipient mailbox include:
Envelope message overhead There is a small overhead for each journalized message, because the envelope journal message includes a plain text report with the original message attached. Unless there are thousands of recipients listed for a particular message, the plain text report adds less than 1 kilobyte (KB) of overhead, in addition to the original message.
Multiple journalized messages If expansion servers are used for a distribution list or alternative recipients are added as a message flows through your system, there will be multiple instances of the same journal message that each report different recipients. Calculating the overhead that this produces is difficult because it depends on whether your organization uses expansion servers or hidden distribution lists and the habits users have for sending their mail.
Storage group configuration As much as possible, minimize the number of storage groups per mailbox database.
As for configuration of the hard disk, follow the general recommendations specified in the Exchange Server 2003 Performance and Scalability Guide. Additionally, the Exchange Server 2003 High Availability Guide provides detailed server sizing recommendations.
Again, only complete testing in a lab and careful monitoring in production will provide accurate sizing data.