Ssd vs spinning hard disk

Documentation says “spinning hard-disks can also be used with some performance penalties”, but for mass import how much slower will this be? Like 1% or 50%, assuming that cpu is not a bottleneck? Or is it likely that the CPU, WILL be the bottleneck, I am trying on a dual cpu dell r740.

Thanks

Are you using more than one harddrive in Raid?
I have 2 harddrives in Raid 0. Don’t know if that would be a bottleneck or not.

Well I guess the question is aimed at what is a more common bottleneck - hd spin speed vs ssd or cpu. I have a sneaking suspicion that cpu speed matters more for indexing, especially on larger databases - small ones I think a little slower won’t matter.