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Comment by jonhohle | Hacker News Reader

This looks incredible. Is it possible to expose a full PCI interface from an NVMe slot? I have an old SAS controller that I want to keep running. If I could do that from a PI, that would be incredible.

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If you want to use SAS with the Pi, I've only gotten newer generation Broadcom/LSI cards working so far—see my notes for the storage controllers here: https://pipci.jeffgeerling.com/#sata-cards-and-storage

Incredible resource, thanks! I’m currently using an older MegaRAID card, but could upgrade if I can find a reasonable configuration to migrate.

> newer

Which is probably for the best - I don't know how these newer cards behave, but a commonality of all the older RAID/HBA cards seems to be "no power management allowed". Maybe they improved that area, because it's pretty unreasonable for an idle RAID card to burn double digit Watts if you ask me...

The 9405W cards I most recently tested seem to consume about 7W steady state (which is more than the Pi that was driving it!), so yeah... they're still not quite as efficient as running a smaller SATA card if you just need a few drives. But if you want SAS or Tri-mode (NVMe/SAS/SATA) and have an HBA or RAID card, this is a decent enough way to do it!

There's no such thing as an NVMe slot, just M.2 slots that have PCIe lanes. NVMe is a protocol that runs on top of PCIe, and is something that host systems support at the software level, not in hardware. (Firmware support for NVMe is necessary to boot off NVMe SSDs, but the Pi doesn't have that and must boot off eMMC or SD cards.)

You can get M.2 to PCI-E add-in-card adapters, yeah - as long as it's an M.2 slot that supports NVMe, not SATA only

I don't see how they could have hooked a 2.5Gb/s Ethernet NIC to the CM4 modules without using up the single PCI-e 2.0 lane other than adding a power hungry, expensive and often out of stock PCI-e switching chip.

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