I install in hdd or ssd for installed computer server

I install a syncloud to where? hdd? or ssd?
if for example I install on a ssd and plugged hdd under syncloud a cloud server machine?
is it possible with that?

Syncloud OS can be on the same disk but it is better to activate a separate disk for apps storage in Settings - Storage.
If you have fast (ssd) and slow (hdd) disk probably it is better to have fast for OS and slow for data unless you stream big data in or somsthing like this.