If you are seeing unreasonably fast read throughput, it is likely that reads are being served from the ARC. If your workload will benefit from the ARC, you may

If you are seeing unreasonably fast read throughput, it is likely that reads are being served from the ARC. If your workload will benefit from the ARC, you may be seeing valid numbers. If your workload will not benefit from the ARC, set primarycache=metadata on the dataset and rerun your test, potentially with a pool export/import or reboot to be sure the cache is cleared. The fact that fio has a bunch of options doesn’t make the tool unreliable. Not understanding the tool or what you are testing makes you unreliable as a tester. The tool is reliable. As you learn you will become a more reliable tester with it.