what setup do you suggest to create a failover backup cluster?
lets say i want to connect to the 2 on site servers with one connection or one path , an if one is down the second is up with the same data on it
Starwind will probably work for this, in fact I had a failover cluster at work using Starwind few years ago, it wasn't worth it. Power loss was the weak point, Starwind had to sync storage after both nodes went down, so we were talking about 3-4 hours of downtime each time power went out for long enough to drain UPSes, no generators unfortunately. We had to spend additional few thousand on bigger UPS units.
So do the math, if the server goes down, would the business lose so much money to justify buying 2nd server? And probably more equipment (UPS, etc.) You can have 4 hour onsite service, Dell I think even offers 2 hours onsite, so best case you could be up and running in 3-4 hours in case of a server failure.
If you plan on going with 10gbit network, you really should be looking at SSD disks, spinning rust will have a hard time saturating that, probably 8-10 disks at minimum.