In a one-tiered architecture, there is no separation between access and data layers. The Instant Messaging server, multiplexor, and sometimes the Directory server are installed in one layer. The following figure illustrates the idea.
To size a one-tiered architecture:
Add CPU for SSL, if necessary.
Add more disks for the increased number of client connections.
Add more disks for each multiplexor.
For specific instructions on sizing Instant Messaging components in one-tiered or two-tiered architectures, contact your Sun Client Services representative.