I recently started doing some higher iodepth (32/64) testing with some high-end consumer SSDs. Of the 6 I tried, one consistently led to fio runs achieving a lower percentage of IO at the requested iodepth. (Every other SSD had >99% of IO at requested depth, This particular drive would get as low as 97%.) I was trying to understand how specific hardware could affect this. It would seem like the only thing an SSD could do to cause lower iodepth_level would be to process data faster than fio could supply it. So I would expect times of unusually low latency. Instead, looking at the runs when this happens, the drive is actually performing unusually poorly. There are some big latency dips from high latencies to much better latencies, but the latencies seen are never anything lower than another better-performing drive. Any thoughts? Happy to share graphs if helpful. Thanks, Nick
