I'm a little perplexed, I just did a slightly different test. Using the SSD volume the dd still yields 300MB/s type results. (This volume does 1.5GB/s writes and 2.02GB/s reads on the FreeNAS shell).
I ran this same test on my SAS volume and attained 151MB/s writes. (This volume does 990-1.02GB/s writes and similar reads).
I find it odd that proportionally it's almost identical, that is 300MB/s is to 2.0GB as 150MB/s is to 1.0GB on the other volume. When the expected result would have been 300MB/s on the SAS volume as well since it exceeds 1GB/s on the FreeNAS shell. Makes me think there is some sort of ratio based issue going on here.
I'll give NFS a try soon.
I ran this same test on my SAS volume and attained 151MB/s writes. (This volume does 990-1.02GB/s writes and similar reads).
I find it odd that proportionally it's almost identical, that is 300MB/s is to 2.0GB as 150MB/s is to 1.0GB on the other volume. When the expected result would have been 300MB/s on the SAS volume as well since it exceeds 1GB/s on the FreeNAS shell. Makes me think there is some sort of ratio based issue going on here.
I'll give NFS a try soon.