How to get files to be written evenly on striped drives?

Hi, I 2 x 3TB WD HDD's striped into one empty drive under Windows 7 and whenever a program is writing files onto it (~200 GB in size) it's not being written equally. It's only being written on one of the drives at least that is what resource monitor and other disk monitoring tools are showing. Some files are written on the second disk, but the two disks are never stressed at the same time. I'd expect files to be written onto the striped drive to stress both disks to utilize the speed advantage. What am I missing?

This from Data striping - Wikipedia, the free encyclopedia seems to speak to that as somewhat normal:

Advantages of striping include performance and throughput. Sequential time interleaving of data accesses allows the lesser data access throughput of each storage devices to be cumulatively multiplied by the number of storage devices employed. Increased throughput allows the data processing device to continue its work without interruption, and thereby finish its procedures more quickly. This is manifested in improved performance of the data processing.
Because different segments of data are kept on different storage devices, the failure of one device causes the corruption of the full data sequence. In effect, the failure rate of the array of storage devices is equal to the sum of the failure rate of each storage device. This disadvantage of striping can be overcome by the storage of redundant information, such as parity, for the purpose of error correction. In such a system, the disadvantage is overcome at the cost of requiring extra storage.

I get that but it doesn't increase the throughput:



It's writing on one disk or the other but never to both at the same time.

I relocated the array into another machine a few days ago which turned the Striped drive into Spanned which explains the behavior.

Case closed.