Depending on system, your server may have different configurations.
Online Rack Mount Units (1000, 1500, 2000, 2500)
Current generation Online units will have hot swappable trays in the back for (2) SSDs.
*Photos below are from an Online 2500.
Internal are SATA and Power
Internal SATA and Power for Single SSD.
Onboard M.2 SSD. *These are very difficult to reach as the entire mother board will need to be removed.
May have an onboard M.2 SSD or SSD similar to the Studio unit.