Supermicro Backplane BPN-SAS2-846EL1 Fan Control

Breit

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Apr 13, 2019
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This topic may have come up a few times, but I did not find a definitive answer, so here is my question: Is it possible to monitor (and control) fans hooked up to a BPN-SAS2-846EL1 backplane?

I have a CSE-846 case with said backplane and a X9DRi-F mainboard installed. For the sake of quieter operation, I'm in the process of replacing the fan wall with a custom build one sporting 6 Noctua NF-F12 industrialPPC-3000 fans (for increased static pressure). The mainboard has 8 fan headers, but I now have 10 fans in the case and don't necessarily want to use y-splitters.

There is a I²C header on the backplane, where the manual says this can be used to monitor and control the fans?!Screenshot 2021-01-02 140903.png

The mainboard also has such a connector, but connecting those 2 does not make the fans run any slower nor do the fans appear somewhere in the IPMI interface of the MB.

Edit: Cable used: Supermicro CBL-CDAT-0601
 
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Breit

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Apr 13, 2019
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OK, so I'm fiddling around with sesutil (FreeBSD) and am able to at least make the fan speed visible. When connecting one of the fans to the FAN_3 header on the backplane, this comes up in sesutil:
1609595980673.png

Still nothing in IPMI though. No fan control either.
 

Breit

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Apr 13, 2019
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So I re-checked everything and figured that sesutil is only reporting fan speeds if the I²C cable is not connected. If I connect the cable, the fan speeds through sesutil says '0 rpm' and its status says 'Not Available'. It seems that the fan control is indeed handed over to the mainboard (or disabled) upon connecting the cable. However the MB does not seem to know what to do with it.

Does anyone know how to use the mainboard I²C header or if this is even possible?
 

penetal

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Mar 14, 2021
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Hei, I am trying to control the fan speed of the fans in my sc847 which has 2 backplanes, one being the BPN-SAS2-846EL1, I am using TrueNas Scale so it is linux based, but I am hoping we can help eachother.

I am able to get some response when using sg_ses --index=coo,0 --set=speed_code=1 /dev/sg10 but after a short while (seconds) the fans are back up to ear murder speed.

I am not sure where to go from here. I saw some random doc for a different backplane that has to enable IDENT to disable the smart fan function ( page 61 ), I tried that just to see and the fans act the same (spin down for a few sec then back up).
 

Breit

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Apr 13, 2019
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To be honest, I completely gave up on the issue. This might be a bit off-topic, but I figured even if I could control the fan speed through the backplane, I still need to make the fan speed dependent on temperatures and that probably would not work anyways. So I decided to build my own solution to the problem:
I had my design for a new replacement for the fan wall frame with 120mm fans manufactured with all the screw holes and threads in the right place to mount it instead of the original. The finished product looked like this:
IMG_20210111_142439.jpgIMG_20210111_165742.jpg

I then hooked it up with 6 Noctua industrialPPC 3000rpm fans, as described above. I connected them in pairs with Y-adapters so that I only need 3 fan headers on the mainboard (FAN3, FAN4 and FANA), but routed the sense pin from the second row of fans to the backplate fan headers.
IMG_20210111_190434.jpg
This way the motherboard can control each duo of fans through its PWM header, but the rpm sense from the first fan goes to the mainboard and the sense from the second fan goes to the backplane. Now I can read the fan speeds also through the backplane if I wanted to. I guess I'm fine with it. Not ideal, but better than nothing?
 
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penetal

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Mar 14, 2021
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The temp should show up as normal temperature for disks so it would just be a simple script to control it with that as the base for the speed level, however I can see how this is easier, I have 3d printed out new cages for the fans so some 80mm noctua fans will fit and will be using that at least until someone is able to help me control the fan speed via the backplane.

I have the 45 drive version so there is no motherboard in mine, it is just a simple JBOD so your solution wont be possible for me.
 

Breit

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Apr 13, 2019
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Ah, I see. Since you have no mainboard, does the power distribution board in your JBOD case have an I²C connector? As I understand the documentation from Supermicro (allthough it is a bit vage about that), the I²C connector on this backplane is exactly for this purpose. Do you have the I²C from the backplane connected to this board?
 

penetal

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Mar 14, 2021
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I am not 100% sure, but before I break my back taking it out of the rack again, where would I connect the cable to? There is a small power board in there, but no "escape" for any cables other than the sff cables to connect to another computer, so if they need to go from inside the chassis to inside the storage node and connect to the motherboard there it would be a very janky solution of drilling holes and making it very very hard to take the boxes out of the rack.

I think the I2C is connected here, but this board dosent seem to give me much option when it comes to control or config:

20210211_183951.jpg
 

Breit

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Apr 13, 2019
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So you have the version with the CSE-PTJBOD-CB2 board, which does not have IPMI and thus can not report any vital system data (fan speed, power supply info, temperatures etc.). There is another power board available from supermicro which has it's own IPMI chip and a LAN interface for it which is called: CSE-PTJBOD-CB3
As fas as I understand it, this has I²C connectors for all the backplanes and you can control the fans through IPMI as you normally would if there were a mainboard installed in the chassis.

So the only option would probably be to see if there is further progress to be made with controlling the fans through sg_ses as you initially tried. But most of the postings about it seem to suggest that it does not work as expected.

If you only want to reduce the fan speed, you could use an inline fan controller like the Noctua NA-FC1 to set the PWM duty cycle to something lower than 100%. I used those prior to my fan wall update to simply reduce the maximum fan speed. The fans are still controllable using this piece, but the duty cycle is simply divided by the factor you set on the fan controller.
 

penetal

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Mar 14, 2021
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I am not planning on using all the hdd slots so I just added in a noctua low noise adapter on each fan, and unless the disks fry due to it that is the end of the story I think.
 

Jebusfreek666

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Feb 6, 2020
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I had my design for a new replacement for the fan wall frame with 120mm fans manufactured with all the screw holes and threads in the right place to mount it instead of the original. The finished product looked like this:
View attachment 17882
When you say you had it manufactured, did you have somebody make this for you? I don't have a way to get all the specs with precision currently to have this fabricated. If there is some way you could point me in the right direction to have another one of these made I would really appreciate it! I don't really want to go the whole "zip ties and weather stripping" route if I can avoid it.
 

penetal

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Mar 14, 2021
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When you say you had it manufactured, did you have somebody make this for you? I don't have a way to get all the specs with precision currently to have this fabricated. If there is some way you could point me in the right direction to have another one of these made I would really appreciate it! I don't really want to go the whole "zip ties and weather stripping" route if I can avoid it.
I realize this might not be good enough for you, but as he shows in the video it should work well and be pretty cheap, with the bonus of sound+vibration dampening:
 

Jebusfreek666

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Feb 6, 2020
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I realize this might not be good enough for you, but as he shows in the video it should work well and be pretty cheap, with the bonus of sound+vibration dampening:
That is kind of neat. I'd like to see the melting/combustion point of that foam though. Id be worried if it tipped over, or if a small bit from a cut area got in somewhere it shouldn't and caused problems. Unfortunately, I don't think this will work in my situation. He's using the 847 which must be slightly wider than the 846. According to everything I have seen, 3x 120mm fans zip tied takes up almost 100% of the room across the inside of the chassis. That rules out the supports in between the fans, although I suppose you could cut it so it only had fan support on the top and bottom. But I think it would reduce the rigidity a lot!