Running ZFS With CAM-based ATA On FreeBSD 8.1

When looking at eight threads of 32MB random writes, the CAM-based ATA infrastructure provided no major performance benefits.

When using 32MB random writes but with 16 threads, the performance of CAM-ATA actually regressed where the old infrastructure was 65% faster than the new implementation with NCQ support.

Even with just four threads of 128MB random writes, the CAM-based ATA infrastructure regressed to the point where the stock ZFS disk performance with the FreeBSD 8.1 kernel was 3.36x faster.