Any idea why those two drives are dramatically slower than the rest?

Submitted ⁨⁨1⁩ ⁨day⁩ ago⁩ by ⁨Lemmchen@feddit.org⁩ to ⁨selfhosted@lemmy.world⁩

https://feddit.org/pictrs/image/3bed4b9a-2f2e-4332-8f64-c919afabaa21.png

I have eight identical drives connected to a LSI 9207-8i.

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:
Image

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?

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Comments

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CompactFlax@discuss.tchncs.de ⁨1⁩ ⁨day⁩ ago
Without googling the specs, are those two on a different channel?

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- Lemmchen@feddit.org ⁨1⁩ ⁨day⁩ ago
  Yep, that was the issue.
  
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- Tolstoy@lemmy.world ⁨1⁩ ⁨day⁩ ago
  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
  
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- jrgd@lemmy.zip ⁨1⁩ ⁨day⁩ ago
  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.
  
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northendtrooper@lemmy.ca ⁨1⁩ ⁨day⁩ ago
As a dude from the peanut gallery still learning, this was an interesting read. Never thought about the importance of what channel the sata cables are plugged into.

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- MuttMutt@lemmy.world ⁨1⁩ ⁨day⁩ ago
  It’s one of the reasons why getting a SAS controller is really nice, backplanes make it even better.
  
  I was preforming a burn with 10 X 8TB drives on a controller that already had a couple operating ZFS pools totaling 18 X 4TB drives and a couple SSD’s and there was no slow downs. A SAS3008 controller can support over 6000 MB/s and has a PCI Express X8 3.0 bus.
  
  I’ve been building my servers and network out of old enterprise gear for a while now. It uses more power but the things you can do are truly amazing. Sadly the ai boom drove prices way up compared to a couple years ago, what I bought for 900 in 2024 is running around 1500 today.
  
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cabillaud@lemmy.world ⁨1⁩ ⁨day⁩ ago

What are “d/s” and “f/s”?

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Lemmchen@feddit.org ⁨1⁩ ⁨day⁩ ago

I actually needed to look that upyself, since I didn’t know either. So, thank you, I’ve learned something new because of your question.

          d/s    The number (after merges) of discard requests
                 completed per second for the device.

          f/s    The number (after merges) of flush requests
                 completed per second for the device.  This counts
                 flush requests executed by disks. Flush requests are
                 not tracked for partitions.  Before being merged,
                 flush operations are counted as writes.

man7.org/linux/man-pages/man1/iostat.1.html

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