Intel Core i7 processor
16GB memory
512GB storage

For example:

 15-inch MacBook Pro 2017:
Touch Bar and Touch ID
2.9GHz Processor 
512GB Storage
2.9GHz quad-core 7th-generation Intel Core i7 processor
Turbo Boost up to 3.9GHz
16GB 2133MHz LPDDR3 memory
512GB SSD storage1
Radeon Pro 560 with 4GB memory
Four Thunderbolt 3 ports
Touch Bar and Touch ID

Virtual Box for OpenStack Requirement

 1 * Controller:

Memory : 8G
Storage : 256G
Network : 4 (extenel, admin, tunnel, net)

1 * Compute:

Memory : 4G
Storage : 256G
Network : 3 (admin, tunnel, net)