PowerEdge T640 Supported Drives

Internal drive bay and hot-plug backplane:
Up to 16 or 32 x 2.5” HDD: SAS, SATA, Near-line SAS SSD: SAS, SATA
Up to 8 or 18 x 3.5” HDD: SAS, SATA, Near-line SAS SSD: SAS, SATA 

Chassis with up to 16 x 2.5" drives with up to 8 NVMe also available.

Datasheet: T640 spec sheet