What is the best practice for physical deployment of data marts?

Question

We are just starting to get into business intelligence at our company. We have some architects who are designing our data warehouse and also our data marts. They are using star schema for both designs.

The architects have stated that the design they are using for the marts is the same, that we just need "another copy" of it for whichever customer wishes to query their mart and that the data may differ per mart.

We only had one mart to start with. This was one AIX LPAR, one DB2 database instance, and one database, with one schema.

Now we have requests for three more data marts. What is the best practice? Should these be different schemas within the same database? Should each mart be a separate database within the same instance? Should we have separate databases, separate instances?

What is the best practice here from a physical deployment and maintenance perspective? Or what guidelines are used to define when it should be which option?