Storage options, from the manual: Your computer supports one 7.5 mm or 9.5 mm hard drive and two M.2 2230/2280 solid-state drives/Intel Optane storage. One 7 mm or 9.5 mm hard drive SATA AHCI 6 Gbps Up to 1 TB Two M.2 2230/2280 solid-state drives/Intel Optane storage   You can either replace the SSHD with a 2.5" SATA, or if you have only one M.2 drive, you can add an M.2 NVMe SSD to the system.  Check to make sure the necessary mounting hardware is present. You can source SSDs from a host of reputable suppliers -  WD, Samsung, Crucial, and many others.  
Hello all i am reaching out to you with request for advise. I am proud and happy owner of Alienware Area 51m with following storage configuration: 256GB PCIe M.2 SSD + 1TB (+8GB SSHD) Hybrid Drive While i am happy with primary SSD disk, i would like to replace SSHD with another SSD. 1) Is it possible? 2) What type of SSD disk will be compatible and able to replace SSHD? 3) Optionally, do you have good experience with any specific vendor / model of SSD in 1T-2T capacity range? Thanks in advance
Area-51m R1, replacement of SSHD drive