HDD Power and PSU

TrueNAS General
1

Hello Guys,

For the info, i’m using a tower chassis and that has 16xSeagate EXOS X16 16TB disks and the PSU i’m using is from Antec Signature Platinum 1300W. From my check, Antec is a rebranded but the OEM is Seasonic. Here’s the exact layout how the drives are connected:

2xSATA (400mm+115mm+115mm+115mm) - 4 connectors on each cable, a total of 8 connectors
1xSATA (350mm+150mm+150mm+150mm) - 4 connectors

TOTAL: 8+4=12.

So, i had to use 1xSATA (350mm+150mm+150mm+150mm) - 4 connectors (from a different unit, but same exact model). Now, i do have the 8+4+4=16 connectors. This becomes 4 cables in total which is connected to the following PSU ports:

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Please note that no other SATA device is connected to the system. The system is equipped with a Supermicro X12SPA-TF Motherboard, paired with Intel Xeon Platinum 8362, has 8x32GB 3200MHz ECC RDIMM RAM, and no extra devices are present/installed on this system except for an LSI 9400-16i HBA card (flashed to IT mode) and a 25GbE NIC (E810-XXVDA-2) and near about 12 FANs which are 3000RPM (Noctua PPC).

Here are the voltage information from the official site:

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If anyone is interested, here is the link to the product page:

I’ve a few questions regarding this setup

I know that this could be dangerous and if necessary precautions are not taken, it can lead to short circuit, overload PSU, trip randomly or even catch fire. I’m also aware that this is why rack mount chassis are more preferred and the biggest advantage for such chassis is the airflow and backplane and easy power distribution. However, at this moment, this is what i have and that i could purchase.

Previously, when i read about the power sizing, i was bit afraid and i guess tug who suggested me to use Kill a watt to measure and then proceed. However, at that time the setup was not fully complete and i was just planning on the parts and kept buying the parts one by one as my budget allowed.

So, are my drives safe and is the PSU enough to power up all the drives, especially when i boot up the system? Until now, i’ve not tried to connect all the 16 HDDs together as the parts were not complete, but now i’ve all of it!

Also, recently, i came to know about staggering. From the Google, i came to know that it is a feature that allows the HBA to spin up the HDDs in a sequence so that the PSU is not overloaded and does not goes out of power when the system is intializing/posting/booting. I’m not sure if this feature is supported by the PCH and whether my HBA supports it or not.

I’m bit concerned and afraid about the data safety and also on a hardware safety side as well. Please advice some.

Thanks

2

Why don’t you simply measure the 12V rail voltage and amperage with a multimeter during startup and high workload scenarios? But my understanding is those drives draw 10.2W peak at 12V so that’s 163.2W (13.6A) about 1/8th of what that PSU can provide. Also that PSU has overvoltage, over current, short circuit protection and a single 12V rail so I wouldn’t be too worried as long as everything is cooled correctly and connected securely.

1 Like
3

You said you have a Kill-A-Watt, so use it.

If I were to collect scientific data about it, unfortunately this does not measure only the 12 Volt and 5 Volt rails, and if you had a proper DC Amp meter, you could take these measurements on a line by line basis, the very best way to do it, but if all I had were a Kill-A-Watt, I would:

  1. Start with the system in a minimal configuration (maybe 6 drives installed).
  2. Using the Kill-A-Watt, when powering on the system monitor the WATTS, record any peeks.
  3. Using the Kill-A-Watt, place it on Power Factor (pf) and record the reading. This is how efficient the power supply is being overall. The closer to 1.0, the better, but do not expect to get a 1.0. This is just good information to know right now.
  4. Power down, evaluate the results. Have you reached the maximum for the power supply? I would honestly shoot for 80% of the power supply capacity. You are not using the CPU heavily right now so you must take that into account.
  5. Slap in a few more drives, repeat the steps.

For those not sure what this means, it means that every manufacturer uses their own wiring pattern for the power supply connectors. Just because it physically plugs in does not mean it is wired for that power supply. This is risky, even if it is the same power supply manufacturer. You need to ‘ring’ out the lines, make sure each line is proper. How many times have I seen someone burn out a power supply because “The connector fit so I assumed…”. It can be expensive if you place +12VDC on the +5VDC line to the motherboard for example, and that can happen by back feeding through the newly added power connector. Be careful if you ever use a connector that didn’t come with the power supply.

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4

Yes, but what about the 5V power draw? That becomes 6.3Wx16=100.8 (20.16A). As per the PSU datasheet, it can do 25A, so quite under the limit. But what about the Motherboard also using the 5V Rail?

Yes, i tested like 5 HDDs and the uptime was 7hrs straight (sometimes idle) and the temps reported for the HDDs in TrueNAS were like 27-28c for all the drives and the starting temps were 23c.

5

Thank you again. Will do this for sure!

Oh yeah, i have heard cases like that. But, like i mentioned, i had two identical models, same batch, so i used one more SATA cable from the other one. I guess as long as the brand and models are identical and you have verified the connection, its all good in place.

6

Power factor and efficiency are two very different concepts and Im not sure what reactive loads we’re worried about to be measuring power factor. That PSU can easily provide 100% rated power at any comfortable room temps (e.g. below 50oC) and either way, its overrated for the use case as there is no way that system even under 100% load will get anywhere near 108A on the 12V rail and 25A on the 5V rail continuous or peak. Not even close.

7

You’re misreading the datasheet. The HDDs don’t use 6.2W on the 5V rail, that’s not how the datasheet is to be read. The 6.2W relates only to the 12V rail and is related to the random read / write power draw, with 10.2W being the max. The 5V line is only for the HDD logic and will be mA max per drive - so nothing to worry about at all. You won’t get anywhere near to 25A (125W) on the 5V rail.