Bahmni will run smoothly on a server with the following minimum configuration. The following server configuration is for running complete Bahmni with all sub-systems, i.e. OpenMRS, OpenERP and OpenELIS.
CPU - Quad core (8 core, if in future you would want to run PACS integration from the same server)
Memory - 8 GB (16 GB, if in future you would want to run PACS integration from the same server)
Hard disk - 500GB (doesn't include the disk space needed for PACS integration or if you plan to upload a lot of files/images)
If you are running on OpenMRS sub-system then 8 GB is more than enough.
SSD drives perform much better than SATA, but is slightly expensive.
500 GB has been mentioned above not because the system needs that much space but because it is standard specs. 150 GB should be more than enough in most cases.
It is highly recommend to have one more machines as a backup machine that can take over in the scenario when the main server fails due to hardware / electrical issues. This backup machine can also be used to store database backups or old log files, and for load intensive reporting.
The minimum hardware requirements for test installations are 4GB RAM and 2 CPUs. 8+GB RAM and 4+GB swap space are recommended though.
Installations with 4GB should skip the installation of OpenERP and Bahmni Reports:
bahmni -i local --skip openerp,bahmni-erp-connect,bahmni-reports install