How are the 15 drives powered at startup

First of all, I love the design and I’m definitely getting one for myself soon.

However, after extensive research, I’m still confused about a few things.

SATA power can deliver a maximum of 54W and 4.5A per connector. Given that the 750W PSU in the configurator has four SATA power connectors, this totals 216W and 18A. The 12V rail in that PSU can handle 62.5A.

A 16TB Seagate drive requires 2A at startup, so 15 drives would need 30A. Wouldn’t this configuration overload the SATA power cables and connectors?

I’ve considered staggered startup, but it doesn’t seem feasible with Unraid.

I hope someone can clear up my foggy mind, as i am really scared of the saying “Molex to sata. lose your data”

The HL15 doesn’t use the SATA/PATA cables that come with the RM750e. It has a small custom PDU board that handles distributing power to the backplane and the fans. It gets its power from all four of the SATA/PATA outputs of the PSU;


I can’t get a good picture of it, but all four of those ports, all 24 pins, provide power for the backplane and fans via a power distribution module.

Staggered spinup should be configurable in the HBA unrelated to Unraid. See this video @ 3:55:

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Thanks for the fast reply!

Seems like I worded it slightly different/wrong, but I indeed meant the SATA/PATA connectors. Each of those is rated at 54W or 4.5A (4x4.5=18A) The PDU you mentioned is fed by 4 molex connectors.

You said; “It gets its power from all four of the SATA/PATA outputs of the PSU”
which would be 18A/216W

So you are saying that is the maximum each of these cables included with the PSU can handle?


I’m not sure that’s right. I think that is the spec for the SATA connector that plugs into an individual drive, not one of the four “SATA/PATA” modular outputs from the PSU.

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That sounds feasible, Thanks for clearing that up.

That spec is for each supply rail for each connection. This is why one should not try to go more than the connections supplied on an individual cable for hdds. What I mean by this… That is why the back plane is split into 4/4/4/3 with each having its own supply from the PSU. If you try and plug all four PATA connections into one, you will trip the OCP.

With that being said, if you look through 45Drives blogs, they did a test where starting up 60 drives all at once peaked out at 51 amps. The requirements for a HDD are max requirements. Most current drives require much less than the 2A at startup.