PowerEdge R660xs Supported Drives

Internal drive bay and hot-plug backplane:
Up to 110 x 2.5” HDD: SAS, SATA, Near-line SAS SSD: SAS, SATA 
Up to 4 x 3.5” HDD: SAS, SATA, Near-line SAS SSD: SAS, SATA 

Datasheet: R660xs spec sheet