I'm starting to run out of space and room in my rack for drives. I currently have an Inter-Tech 4U 4129L with an array of 14 drives (incl. one for parity), plus an nvme, ssd cache and a hdd cache all working quite well with an Zalman ZM750-ARX PSU. The drives are a mix of shucked 8TB WDCs, 16TB Seagate DC and WDC DC drives totally 152TB, and yes, I'm running out of space.

 

I bought the Inter-Tech 4F28 (imgur), as it can hold 28 3.5" plus 6 2.5" drives (two on either side of the drive cages and two side mounted in the rear compartment) without thinking of PSU, but just needing more drive space. I plan to populate it with WDC 16tb or 18tb DC drives, which usually pull operationally 5V/0.5A and 12V/0.57A, but would like to port over my existing drives which based on the drive spec pull 9.2A on 5V and 9.8A on 12V.

 

Yes, I have been reading a lot here, reddit, and many other communities, reached out via DM to a lot of OPs to figure out their set up's, and found that most just only look at the PSU wattage not amps or just plainly ignore amps, staggered spin-ups, max connections on sata cables, and far too many seem to underpower their systems.

 

Personally, I don't need a high-spec'd CPU or motherboard, I currently use a Gigabyte H97-D3H-CF and an Intel i7-4770 with 32gb, which is more than enough for storage and running a few dockers. The controller is a Adaptec 71605 in HBA mode, and I don't see any options in the controller BIOS for staggered spin-up.

 

The short question(s):

- How many drives do you have and what's your cabling/PSU?

- My Zalman ZM750-ARX delivers 5V rail 22A 120W and 12V rail 62A 744W (80% load would be 5V/17.6A/96W and 12V/49.6A/595W) is it enough?

- Should I get a 2nd PSU, just to be safe?

- What's the best mounting options for a 2nd PSU considering the case/any regular 1 PSU ATX/4U case?

 

Am I overthinking this? Did my Googling just make the simple decision a lot more complicated?

 

I won't power up 28 disks by one PSU even all seems within spec.

 

The reason

1. 5v will be the hardest part, always marginal.

2. PSU have lifetime and degrade with time, you generally won't know which day will got trouble.

3. If PSU fault, it may affect all disks and loss everything.

 

I currently run Unraid in 3U rack with 16 disk + 2U rack as disk 12 disk enclosure, so pretty safe.

 

For your case, If only one PSU, I will use 12v connect to a DC-DC module to provide extra 5v to drive half no. of disk. In fact, your PSU 5v also come from DC-DC module inside the PSU that use 12v too.

 

 

Edited February 15, 20224 yr by Vr2Io

Could you clarify what you mean by the DC-DC module and that there's already one inside?

Like most PSU, 5v and 3.3v come from stepdown DC-to-DC converter and draw the power from 12v rail. Two small pieces electronic module.

 

 

 

 

 

 

 

Edited February 15, 20224 yr by Vr2Io

Ah, I get it. In essence I could make an EPS or PCI-E 8pin to a step-down 12V>5V and 12V>3.3V and then to SATA, or just 5V and Molex.

 

However, I seem to be unable to one in Europe.

I managed to find some, even higher rated 12V to 5V 10A converters, and coincidentally also some chia miners that use the same method to split the power off EPS and PCI-E.

4 hours ago, PeterDB said:

or just 5V and Molex

Correct, btw need soldering and wiring .... only suitable for DIYer. So plan B was two PSU.

Edited February 15, 20224 yr by Vr2Io

yeah, I spent a couple of hours to see how to get this done correctly, and even custom ordering the cables, so they are made properly... cost is more than an second PSU. Easier to get an Add2PSU and use a second PSU.

 

Thanks again for the help!

 

Last question: You mention you run a 3U and 2U as a diskshelf, how are you ensure the power on between the two?

30 minutes ago, PeterDB said:

Last question: You mention you run a 3U and 2U as a diskshelf, how are you ensure the power on between the two?

The 3U are Unraid main unit, just 2U is enclosure. I add a electronic wifi module which connect to PSU, case button and LED. So I can power on off by button or mobile apps. ( Also need DIY )

 

FYR, power draw 200w - 500w total, depends on disk and CPU loading.

 

Something like that https://www.amazon.com/dp/B0912S2T38/ref=cm_sw_r_apan_glt_i_WTYCD7V3KE0HCDRFV0QP

Edited February 15, 20224 yr by Vr2Io

Interesting! Why honestly, why not just use the Add2PSU and a molex connector between the cases?

2 hours ago, PeterDB said:

Interesting! Why honestly, why not just use the Add2PSU and a molex connector between the cases?

The reason is enclosure disks not part of arrary, only power on if I need to access.