said by trparky:I don't ever remember benchmarks for hard drives being this piss poor. What has happened to hard drives lately?
Did you notice that your screenshots show a benchmark for a WD2002FAEX which refutes your own statement?
So really, the question shouldn't be "Why are MHDDs getting worse" (they aren't), but instead "Why do my ST31000528AS and HTS725050A9A364 perform so significantly worse compared to other MHDDs?"
There isn't enough data provided by you at this time to answer the latter question.
Also, be sure to keep something in mind: while I can believe the read benchmarks for all of these drives, I cannot necessarily believe the write benchmarks. The reason is that you have active filesystems on the drives, so doing sequential LBA writes would completely stomp all over the filesystems. This means the benchmarking software in question is probably doing something like creating a sparse file of an extremely large size (say 25GBytes), does an lseek() to offset 0 in the file, proceeds to do benchmarked fwrite()s, takes note of the response time, then when finished deletes the sparse file. If that sparse file starts near the end of the drive (meaning around the inner portions of the platters), it's going to show worse results than if it starts LBA 0 (the outer portion of the platters). In turn this means the filesystem layer plays a large role with regards to the performance data shown.
ATTO is another benchmarking utility that does this (which is fine, I use ATTO all the time for this exact purpose), while HD Tune Pro does it right -- the "Benchmark" tab does actual LBA reads/writes (which is why you can't have a filesystem on the drive you're write benchmarking), while the "File benchmark" tab does exactly what I described above.
Welcome to benchmarking software 101, and why I avoid benchmarks.