I'm guessing whatever he used, the RoC simply wasn't tuned for it. Kristian never mentioned what he was using for SSDs or if they were all identical. And the 15% performance hit for sequential reads in RAID 10 doesn't seem too egregious, especially seeing as random reads went up by almost 17%.

120 MB/s for a single drive, or near as makes no difference 3x. In this case, the Pegasus2 M4 hit 355.5 MB/s vs.

If you only stripe across three drives and write parity data to the 4th, it would be pretty challenging to read back faster than 3x the maximum a single drive can muster. I'm not sure why Kristian thought RAID 5 read performance would be higher. The performance scaling actually looks damn near perfect with the HDDs, and indicates that the RoC is actually a beast for the intended workload.

So the SATA (actually SAS in this case) controller and the RAID controller aren't terribly separable. repoman27 - Sunday, Septemlink If Kristian was correct in his guess that there's a PMC-Sierra PM8011 lurking under that heat sink, which is quite likely seeing as Promise uses that chip in several other products already, it's an RoC (RAID-on-Chip).

Pegasus2 r6 atlanta