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Trying to decipher IO options of supermicro motherboard (alien.top)

submitted 1 year ago by draetheus@alien.top to c/homelab@selfhosted.forum

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I'm currently running TrueNAS Core on a Atom C3558 board for typical desktop NAS purposes: https://www.supermicro.com/en/products/motherboard/a2sdi-4c-hln4f

I'm building out a vmware cluster and trying to figure out if I can simply upgrade my existing NAS with a 10GB NIC and a couple enterprise SSDs to provide shared storage for the cluster. I would not want to use my 4 x 10TB RAID-Z pool as vmware storage since RAID-Z is apparently bad for block storage, plus spinning rust is slow on IOPS.

I'm using the builtin 4 SATA ports, but there is a MiniSAS HD port available for 4 extra SATA ports via breakout cable. I was reading the motherboard manual and unfortunately it seems like there is not enough IO to run the MiniSAS HD port with 4 extra drives AND the PCI-E slot at full bandwidth for the 10GB NIC? I'm not 100% sure since the wording is not clear:

This is a feature on the -2C/4C models only. Up to a total of 8 in selected combinations of SATA ports and four lanes on the PCIe slot can be made available at any given time. Mini SAS offers 4 SATA ports from the Mini SAS HD header. The options are [Mini SAS/SATA (3:0)], [PCIe x2/Mini SAS/SATA (1:0)], [PCIe x4/SATA (3:0)], and [PCIe x4/Mini SAS].

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[–] merkuron@alien.top 1 points 1 year ago

Maybe it’s clear this way:

For every 2 lanes you want allocated to the PCIe slot (up to 4), you lose two SATA lanes. Since there are 8 lanes total, but 12 possible lane destinations, they pre-made combinations of destinations that they think would be useful:

All 8 lanes to SATA, 4 onboard and 4 through MiniSAS
2 lanes to PCIe and 6 to SATA, 2 onboard and 4 through MiniSAS
4 lanes to PCIe and 4 to SATA, either activating the 4 onboard ports or the MiniSAS (but not both)