Slow Micron 6500 ION SSD reads but fast write speeds via MCIO x8 port?

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1

Hey folks,

I have dual Micron 6500 ION SSDs connected to an MCIO x8 port that is PCIE Gen 5 capable on an AMD Epyc-powered motherboard (the MZ73-LM0 v 2.x). The server is running Ubuntu Server and the drives are connected via md0 software RAID 0 and formatted as ext4. This is a fresh install.

For some reason, I get acceptable write speeds (5.6 GB/s for RAID 0) but slow read speeds (1.8 GB/s in RAID 0, 750 MB/s for each drive when individually mounted). Any advice on what might be the cause? I’m using dd to write/read 10,000 1Mb files to test the speeds. Any advice on troubleshooting this?

Micron 6500 IONs should be capable of sequential read speed of 6,800MB/s and a sequential write speed of 5,000MB/s

This is a link to the cable I’m using, which I believe I saw Wendell had used elsewhere on here: https://www.amazon.com/gp/product/B0CCV4PXV8

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Thanks for posting this thread and sorry for resurrecting it. I was looking for information on how to use those ports. I’m going to order one of these exact same boards this week. I wanted to use a ZFS mirror on NVME/U3 storage and the board only has one NVME slot… The GIgabyte manual, for the MZ73 series motherboards, is not great… :expressionless:

I now know I need a: PCIe Gen5 MCIO x8 (SFF-TA-1016) 74P to *2 Multilink PCIe drive receptacle (SFF-8639) 68P w/15P Power cable. This helps a lot (knowing the interface codes for each end)!

Did you manage to sort out your speed issues?
It does state in the manual:
2 x MCIO 8i with 4 x Gen5 NVMe or 16 x SATA ports, from CPU_1
So perhaps the speed issue is something to do with using a dual CPU setup??

Thanks
Bob