Windows 10 Upgrade..... Option to erase 2 hard drives?

[YoshiBonifacio]

I never upgraded with 2 hard drives before, but when i do will it do a clean install on both hard drives or just on one?

 

[TechyInAZ]

If your drives are in a RAID then windows will see it as one drive... If you didn't raid, then you'll have to select which drive to put it on.

 

[USAFRet]

I never upgraded with 2 hard drives before, but when i do will it do a clean install on both hard drives or just on one?

When you Upgrade, it will just replace the OS you currently have, where it is.
If you want to do a clean install after, you can choose which drive to install it to. But you should really only do a clean install with one drive connected.