I plan on writing a guide on how to build a rudimentary DAS for cheap mass storage using a SAS Expander. The x8 slot on the SAS Expander doesn’t need to be connected to a active computer in order for a SFF-8088 cable to be connected to the external port and communicate with an active separate box though a HBA/RAID Controller.
The initial guide I had followed had you mount an unpopulated motherboard in an enclosure and connect the PSU. Even though a CPU & RAM would be missing and the system would never POST it would power the PCI_e slots enabling the SAS Expander to work.
What I had in mind was to take a page out of the cryptominers book and use a USB PCI_e 6-pin powered riser:
It could be connected directly to the PSU and in theory that’s all ther’d be to it.
So in this are my questions:
Can anybody say the viability or reliability of powering a SAS Expander off one of these?
Would it be inadvisable?
Are they reliable? (I think I know the answer to that one in which case would the reduced power draw help any?)
Does it power all the power pins at the same voltages as it does on a motherboard? Or have they been made specific to only the pins a GPU would require? Or is all of that wrong and it doesn’t matter it’s universal?
1 yes this is how those devices work
2 kinda i dont trust these expanders for any length of time miner failure rates arent good
3 no
4 this is a tiny bit beyond me @PhaseLockedLoop i dont know bout this exactly i expect it to just be the same as its the same psu but im intoxicated so this maybe jsut poop
I’ve created custom molex power cables for my psu to power an expander in my old NAS setup.
It’s perfectly viable and actually really convenient, but is not something to get into blithely or without taking the time to learn what not to do. PSU cable are NOT interchangeable between brands or (usually) models.
So far so good with the one I setup in my own DAS. Do you have one you would recommend more or do you not recommend SAS Expanders period?
+1 informative
I’ve been doing this type of experimenting and self education in computer technology and general electronics for more than 10 years now which is why I’m being cautious asking for 2nd, 3rd, and 4th opinions instead of going gung-ho and writing up a guide that has people doing things that are inadvisable.
It occurred to me that the pin-out of the SATA/Molex to 6-pin in itself may not be a standard 6-pin connector. In this case I’m not beyond de-pinning a standard PCI_e 6-pin and re-pinning it with the riser 6-pin and moving pins as necessary assuming the metal pins fit inside the housing correctly.
I’m not certain I explained what I meant well enough. I’m asking if these risers are wired up in a way that has them power the connected device identically to a standard PCI_e slot regardless of connected device or if they are somehow made specific to GPU’s only.
The specific SAS Expander card I’m referencing can be grabbed off Amazon for ~$26.
So in some regard it is possible but there are still the questions of do most SAS Expanders run on 12V only just fine, do they require other rails, does PCI_e supply rails other than 12V at all?
Then we’d be back on the question of how dependable is it? I don’t expect enterprise level reliability but something that will work for a couple of years at least for a at home DIYer.
