Martin,
Have you tried looking at the BI 4 Admin Guide / Unix Install Guide / Sizing Doc
http://help.sap.com/businessobject/product_guides/sbo41/en/sbo41sp7_bip_admin_en.pdf
http://service.sap.com/~sapidp/012002523100018604152015E/sbo41sp7_bip_inst_unix_en.pdf
Sizing and Deploying SAP BI 4 and SAP Lumira
Regards,
Ajay