Running ZFS With CAM-based ATA On FreeBSD 8.1
When increasing the thread count from 8 to 16 with the 32MB writes, the performance improvement with ZFS and the CAM-based ATA infrastructure increased by 33%.
The thread count was then increased to 32 threads of 32MB writes, but the performance improvement with this new infrastructure in FreeBSD 8.0+ was 28%.
When upping the write size to 128MB but sticking with 32 threads, the CAM performance improvement was just 15% compared to 28% when the write size was four times smaller.