Can i install 4 drives but JBOD 2 drives as 1 large disk?

[TwoBytes]

As the title says, can you combine 2 drives to one large without the expensive raid card?

 

[Flash SWT]

Yes, OS X supports software RAID 0 (striping) that will combine 2 drives into a single one as seen by the Mac. You can configure it in Disk Utility.

Note however that if either of the two drives fails you will lose the data on both of them.

 

[velocityg4]

Are all four the same size. You could do RAID 10, maybe it is 0+1 but does not really make a difference.

That way if either RAID 0 array fails it is mirrored on the duplicate array.