SAS is calling every service a server. I assume you are referring to a multitier installation.
The metadataserver can be seen as an isolated service
Even that can be made as complicated or simple as you could think of. I would not bother on old release but look at 9.4
SAS(R) 9.4 Intelligence Platform: System Administration Guide That is metadataserver clustering.
SAS(R) 9.4 Intelligence Platform: Desktop Application Administration Guide (desktop DI with connect etc)
you could desing a SAAS: http://support.sas.com/resources/papers/proceedings13/494-2013.pdf (I would do some things different but the concept is good)
The objecspawner is forking processes SP WS etc. (app-servers) this combination is always set up together.
Call it a compute-tier. if you extend that to managed instances it is a grid.
Grid Computing in SAS(R) 9.4 (SAS Grid Topology) that can be managed by LSF with the requirement of shared data locations
Building up with firewall's
Communications Access Methods for SAS/CONNECT(R) 9.4 and SAS/SHARE(R) 9.4 (firewall)
SAS(R) 9.4 Intelligence Platform: Middle-Tier Administration Guide (firewall)
---->-- ja karman --<-----