Is it preferred to have one depot with multiple folders which map to different paths in a workspace. OR multiple folders in one depot that map to multiple workspaces, or multiple depots to multiple workspaces.
Does anyone have any practical advice on the matter?
I've also noticed that when I have multiple folders in a depot that map to different paths in my workspace when i diff from the depot a change in one of the sub folders does not show up in the diff.
Depending on the size of your depots I think it is more a question of taste. We have currently two different depots, but mainly because they are disjunctive in their nature (//sw vs. //data/). The Perforce Knowledge Base says:
The most significant difference with the multiple depot configuration is that, in the Perforce Server P4ROOT directory, each project is stored in its own top-level depot directory (rather than as a subdirectory of a single depot). The multiple depot configuration allows you to use the depot "Map" field to put each top-level depot directory on a separate filesystem, if desired. More on using the Map field can be found in the Command Reference entry for the p4 depot command.
Performance is another consideration in configuring single vs. multiple depots. By splitting projects into separate depots, file paths for many Perforce operations are inherently limited to a more narrow range of files, resulting in reduced need to scan certain database tables. The performance difference is dependent on the particular data sets and usage. For many small installations, there is no appreciable difference. However, for larger installations and for some usage environments, the performance difference might be significant.