I have eight identical drives connected to an ~~LSI 9207-8i~~ ASRock X470 Taichi Ultimate mainboard.
They're currently all running badblocks -b 8192 -c 2048 -p 0 -s -t 0 -v -w /dev/disk/by-id/ata-WDC_WUH722424ALE6L4_[XXXXXXXX] each.
While sda and sdb achieve almost 300MB/s, sdg and sdh struggle to even get to 200MB/s. That's a 50% difference!
All of my drives are recognized as SATA3, confirmed by smartctl -a /dev/sd[a-h] | grep SATA showing SATA Version is: SATA 3.5, 6.0 Gb/s (current: 6.0 Gb/s)
There's no CPU bottleneck either AFAICT:
Any idea what could be the issue of that? Is such a dramatic speed difference to be expected of Ultrastar drives?
Are these drives just bad?
Edit: Mainboard configuration:
Edit2:
Okay, apparently the ASM1061 which provides the two extra SATA3 ports is connected to the CPU via a single PCIe 2.0 x1 lane, which provides only 4gbps (=500MB/s) of raw throughput.
I think I have found the culprit and the problem should disappear once I connect the drives to my LSI 9207-8i HBA card.
Without googling the specs, are those two on a different channel? ie the chipset has 6 and then another chip handles 2 or vice versa
Yep, that was the issue.
While browsing the manual you're on point. I bet the 2 drives are plug into SATA3_A1 and A2. These 2 are handled by an ASMedia ASM1061
Based on OP's edit, that looks correct. Unless OP checks the topology and can make the claim that drives from the main chipset are the slow ones, secondary chipset drives will tend to perform slower, and the ASMedia ASM1061 has several reports online of poor to trash performance compared to baseline.
Best bet if the full performance is necessary out of every drive would be finding a decent quality PCI-E SATA III riser card that doesn't use a known flawed driver chip rather use the two 'extra' ports on the motherboard.