I have one of the SFF units as a file server. There's a 256Gb SSD under the DVD drive and a 2 Tb drive in the floppy bay. I managed to break the SATA connector off the DVD drive so I'm just leaving it in there as a large blanking plate!
I use this to read the SMART data:
https://crystalmark.info/software/Cr...o/index-e.html
Edit: the above isn't the case actually. . I'm going to open it and have a look quick. One min!