I found out that on our current cluster (4x H500 nodes) the maximum write throughput I can get  on a "streaming" profile is around 330MB/s for a single large file that is written in a single thread / single channel mode (SMB3 w/o multichannel). One node can max out a 10GbE link in writes if it gets written to on multiple threads (multiple files) at the same time and does about 660MB/s on a single file if written to in SMB Multichannel. 

Now my assumtion is that the single file single thread throughput is due to the Cluster being limited in maximum stripes with 4 nodes (and therefore maximum number of used disks to store the file). We are about to expand the Cluster to 8 nodes which will dramatically expand the striping. 

But what about the maximum number of concurrently used disks per file in a 8 versus 4 node Gen6 cluster? Does the disk pool size expand when we grow from 4 to 8 nodes? If not, the striping expansion would not have an increasing effect on throughput when max stripes increases from 6+2 to 14+2...

Or am I getting it totally wrong?

If my assumtion is right (and disk pool size will not be the limiting factor in an 8 node cluster), I will see either about a doubling or a little more (14 vs 6 stripes) in throughput in a single file single thread scenario. Correct?