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I have seen examples of home-brew NAS units that use SAS expanders plugged into a host motherboard that has neither a CPU or memory, literally for the purpose of powering the card. If the card doesn't need the PCIe slot, why are they all designed to consume one? HighPoint make a SAS expander that uses a floppy drive power connector and the SCSI bracket mount, though I'm learning it is proprietary in the communication so unsuitable for my needs.

Some example cards with internal/external ports. Interestingly the second card seems to have no pin contacts at all for the slot shape, how it is powered is ambiguous:

enter image description here enter image description here

Would this board be effective at powering such cards? Would there be any missing features or functions?

PCIe power board

J Collins
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  • Did you ever try it, and did it work? A guy over here reported success with something similar: https://forums.servethehome.com/index.php?threads/powering-a-pci-e-sas-expander-without-a-pci-e-slot-theoretically-possible-to-make-an-adapter.14214/post-136530 – rkagerer Apr 23 '21 at 18:30
  • I did try it and it did work and now powers the drives in my server! However the SAS expander car has 8 internal connectors, but two seem to be dedicated to being the host connection, leaving 6 (x4) slots available for attaching drives. I'd love to learn there as a firmware update that eliminated this limitation. – J Collins Apr 30 '21 at 17:26

2 Answers2

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A PCIe card is a convenient form factor for a SAS expander. Most often, the number of internal ports is insufficient and it's easily expanded internally.

Would this board be effective at powering such a card?

Possibly. You're not providing details to that card nor a link to its datasheet.

Zac67
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  • On the 'Possibly'. I gather from this answer that there is no general answer, compatibility will be a function of a number of more detailed factors. I was hoping that an expander going from card mounted internal ports to card mounted external points would only be using the PCIe port for power - in which case power supply capacity is the key question. I will add an example card to the question. – J Collins Feb 24 '20 at 12:57
  • The picture isn't enough to judge. You'd need to look at or provide the datasheet, manual or something else to see if that use is possible. Yes, an expander uses only power from the slot, so if that adapter provides power by itself you're good. The power supply capacity would only be an issue with a *very* slim PSU - I'm sure an expander draws below 15 W. There are expanders in different form factors as well, so it might be simpler to use something different. – Zac67 Feb 24 '20 at 13:10
  • I am asking as the only card I've found not in the PCIe form factor is one using the proprietary HighPoint communications. Can you recommend any? Also if you need the datasheet, I would ask what characteristic you are looking for. – J Collins Feb 24 '20 at 13:12
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https://www.intel.com/content/dam/www/public/us/en/documents/product-briefs/raid-expander-res2sv240-brief.pdf

Intel made this SAS expander card with an RA 4pin power connector to power from cable instead of the PCIe slot, the card has alternate mounting holes so you could stick it pretty much anywhere.

I've used powered riser boards like you pictured for GPUs and the only tricky bits are getting a solid mounting between the board and the GPU to make a reliable connection, and some issues with QA. If you power the riser board directly from the PSU it should manage 15W for the expander card easy. I've used one for a 50W GPU continuous load successfully (ie. Without causing a fire)

Due to the unknown providence of the riser board I'd recommend stress testing it in the open until confident it's not going to fail catastrophically.

Andrew
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