SATA power splitters, how many can you do on 1 SATA power cable?

[John Danger]

How many SATA power splitters can you use on a single SATA Cable?

 

I found some that are like 1 to 5 and the SATA in my case has like 2 connection. So can 1 cable do 10 power cables for 10 hard drives?

 

Thanks.

[Hoopster]

On 11/28/2022 at 7:05 PM, John Danger said:

How many SATA power splitters can you use on a single SATA Cable?

Depends a lot on your power supply and if it has a maximum power draw rating per cable.  My case has an 8 HDD hot-swap cage and it recommends that the power to the cages be from two different PSU Molex cables.  Molex (4-pin peripheral provides power to the cages where each drive plugs into a SATA power connector in the cages.

 

It also depends on how many amps your 12v rail supports.  For unRAID and lots of HDDs, it is better to have a PSU with a single 12v rail that supports the combined power draw of all the drives, CPU and GPUs on startup .

 

Here is an example from a Seasonic PSU (83 amps on a single +12v rail for a total of 996 W):

Edited December 1, 2022 by Hoopster

[John Danger]

1 hour ago, Hoopster said:

Depends a lot on your power supply and if it has a maximum power draw rating per cable.  My case has an 8 HDD hot-swap cage and it recommends that the power to the cages be from two different PSU SATA cables.

 

It also depends on how many amps your 12v rail supports.  For unRAID and lots of HDDs, it is better to have a PSU with a single 12v rail that supports the combined power draw of all the drives, CPU and GPUs on startup .

 

Here is an example from a Seasonic PSU (83 amps on a single +12v rail for a total of 996 W):

 

 

 

Thank you. This is extremely useful information.

 

 

So a single rail means there is like 1 output dividend into all the various power wires coming out of a power supply?

 

How much power do you factor in for each hard drive?  Somewhere between 5-10 Watts?

 

Thanks.

 

 

[Hoopster]

2 minutes ago, John Danger said:

So a single rail means there is like 1 output dividend into all the various power wires coming out of a power supply?

No, there are separate rails for 3.3V and 5V.  It's more an internal circuit thing in the PSU than a wires thing coming out of the PSU.

 

Hard drives will usually provide power draw specs such as these:

 

While reading or writing it draws ~5W.  Although not stated here, the largest power draw is usually on startup.  When unRAID boots, it spins up all disks.   Lets say it may draw 7-8 watts on startup.

 

Unless you have a very large number of HDDs in your array, the amount of power the disks draw is usually not as big a consideration as the CPU and GPU(s) which are a lot more power hungry.

[JonathanM]

Using a SATA connector from the power supply, maximum I would feel safe would be 2 drives, and even then it's not a good idea. The SATA connectors are just a poor design, and you are asking for problems by putting them in a chain.

 

If you use a 4 pin connector from the PSU, they can pass current much better, and it should be safe to run 4 drives from one 4 pin source, assuming the PSU can handle the current.