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No, I get that... and there is a different level between hobbyist projects and larger production projects. Using the existing PoE "infrastructure" makes a lot o

No, I get that... and there is a different level between hobbyist projects and larger production projects. Using the existing PoE "infrastructure" makes a lot of sense in the prototyping stages. But if you're already going through the process to build custom boards for a cluster, then a backplane makes much more sense. We're not talking about a small 4-5 RPi cluster where everything can work off of a single PoE gigabit switch with a rat's nest of cat6. This project is talking about 16 of these blades in a 1U chassis. If you're going to go that far, a backplane isn't a big leap and would save power, space, and make cabling much easier.

toast0 5y ago
The trick is, if your backplane is providing ethernet switching, then you need to provide for different levels of network needs. Some people would be fine with a dumb N + 1 port gigE switch, which would be inexpensive, others will need 10G uplink, some 2x 10G with LACP so there's no bottleneck, some are going to want vlans or other managed switch style offerings, etc. If the PoE power conversion really eats 6W per board though as mentioned in the article, that seems like a lot of power and an alternate power arangement would be a no-brainer.
- deleted 5y ago
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- mbreese 5y ago
  Given the amount of these that will probably be made (I imagine it will be a low number), I could certainly see having at least two backplanes: 1) network passthru cables with power 2) 1G network switch with 1G or 10G uplink I just don't see there being much of a market for these where you'd have to have many more options. But, I think the power option is really a no-brainer... if you have to put passthru RJ45 jacks on the back of it, then that would be fine. At least they'd be in the back and could be pre-wired. I'm tempted to get a CM4 and try to put together something just to see if it would work. I really don't have a problem with much else on the blades as-is (aside from the TPM, I'm not sure what that gets you). I do like the ide of putting an SSD on the blade for storage.
  - toast0 5y ago
    Yeah, I could see a passthrough thing, where you had an edge connector (or something), that was the 8-pins for networking and two for +5V and the backplane was just a +5 rail, and the rj45 jack right next to each slot. As a zero experience with PCB design kind of person, this seems relatively simple. You could make a 'one blade backplane' with a PoE kit for the single/small number of devices case where PoE makes more sense.

toast0 5y ago

The trick is, if your backplane is providing ethernet switching, then you need to provide for different levels of network needs. Some people would be fine with a dumb N + 1 port gigE switch, which would be inexpensive, others will need 10G uplink, some 2x 10G with LACP so there's no bottleneck, some are going to want vlans or other managed switch style offerings, etc. If the PoE power conversion really eats 6W per board though as mentioned in the article, that seems like a lot of power and an alternate power arangement would be a no-brainer.

deleted 5y ago
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mbreese 5y ago
Given the amount of these that will probably be made (I imagine it will be a low number), I could certainly see having at least two backplanes: 1) network passthru cables with power 2) 1G network switch with 1G or 10G uplink I just don't see there being much of a market for these where you'd have to have many more options. But, I think the power option is really a no-brainer... if you have to put passthru RJ45 jacks on the back of it, then that would be fine. At least they'd be in the back and could be pre-wired. I'm tempted to get a CM4 and try to put together something just to see if it would work. I really don't have a problem with much else on the blades as-is (aside from the TPM, I'm not sure what that gets you). I do like the ide of putting an SSD on the blade for storage.
- toast0 5y ago
  Yeah, I could see a passthrough thing, where you had an edge connector (or something), that was the 8-pins for networking and two for +5V and the backplane was just a +5 rail, and the rj45 jack right next to each slot. As a zero experience with PCB design kind of person, this seems relatively simple. You could make a 'one blade backplane' with a PoE kit for the single/small number of devices case where PoE makes more sense.