The goals of sizing your Message Store are to identify the maximum number of concurrent connections your store can handle and to determine the number of messages that can be delivered to the store per second.
Determine the number of store machines and concurrent connections per machine based on the figures you gather by using a load simulator. For more information on sizing tools, see Using a Messaging Server Load Simulator.
Determine the amount of storage needed for each store machine.
Use multiple store partitions or store machines, if it is appropriate for your backup and restoration of file system recovery times.
Sun Client Services is often asked to specify a recommendation for the maximum number of users on a message store. Such a recommendation cannot be given without understanding:
Usage patterns (as described in Using a Messaging Server Load Simulator.
The maximum number of active users on any given piece of hardware within the deployment.
Backup, restore, and recovery times. These times increase as the size of a message store increases.