I’m currently about to build a system, as in I’ve been waiting over 10 days on a 32Gb Optane for a boot drive and LSI 9305 from China while I have all my other components, and I thought to ask about a PSU current concern while waiting.
Currently I have a 1000W Leadex VI ($130), but a forum post, on LTT, indicated that the 20 amps shared between the 3.3v and 5v would be insufficient to support the 18 drives that could fit in my case due to overhead from the motherboard, usb connectors, etc.
They recommended the Corsair “load balancer”, Load Balancer Page ($40) to allow all the drives to be connected.
That said, I wanted to double check their estimation that each HDD requires, in additon to the 12v rail requirement that is not an issue, they also require .5 to .75 amps per drive and just how much overhead would be lost to the motherboard and peripherals from the shared 20a between the 3.3v and 5v.
In short, is this “load balancer” needed, is 20a shared between the 5v and 3.3v enough for 18 drives on top of standard system operations, or do I need a more expensive PSU ($180-240) that can supply 25a shared between 5v and 3.3v. I’d rather not pay 1.5x as much for the PSU if it’s avoidable, but would very much like to hear your knowledge on the matter.
I’m posting here since I asked Google Gemini the 5v amperage needed per drive and it said 0.1-0.3, much lower than 0.5-0.75 amps. I checked the official drive spec sheet to settle things and it only listed power needed in watts.
If it makes any difference, the planned drives are refurbished Ultrastar drives, and I know they use both 12v and 5v power- the only potential constraint is the 5v rail current. Thank you!
Oddly enough I did go through it first. It only referenced 12v amps, of which a 1000W PSU supplies plenty. It only supplies 20 amps of 5v and I’m not sure if that would be sufficient. 12v is the big one, but after someone pointed out 5v being a potential issue I thought to try and ask if it would be, if I should convert 12v to 5v with DC to DC with said device, or if the 5v draw is low enough that it’s a non issue compared to 12v. Thanks!
I pulled up the spec sheet of our two PSUs and retain some concern as while the max amperage on the 5v and 3.3v is the same, the shared wattage on yours is 50W higher for those two rails. I don’t think the 3.3v is used much to my knowledge, so it could very well be fine after all. Please correct me if that’s a bad assumption and I’ll turn on staggered startup just to be safe when I set up everything this week. Thank you again. Hopefully the below comparison from the respective sites will be of help to anyone searching with a similar concern about the limited current on the 5v rail as compared to the 12v on modern PSUs.
I have to say that is objectively impressive. If it’s not too much trouble would you mind briefly talking about your power cabling setup? I’ve read the power limit for SATA connectors is 54W and that SAS drives can draw 18-25W when spinning up, meaning only two- potentially three drives (taking the lowest number) could be added on each SATA connector without staggered startup, but Molex has 132W even if the convention seems to be attaching no more than 4 drives, only using crimped cables, and only using after all SATA power plugs are used.
There’s 2x 2 SATA power connector cables that came with the PSU, 2x 4 SATA power connector cables, and 1 4 connector Molex. While the Leadex VI has universal ports so I can buy more of any type of power cable needed, for example this one at ModDIY and plug them in I thought it best to ask if you went 4-drive Molex to SATA, did 2 or 3 SATA drives per SATA power cable, or what sort of combination thereof you used. Would using the cables with four SATA connectors be safe if using staggered startup? I even read one post of someone putting 5 SATA HDDs on a single SATA power plug using staggered startup but it didn’t go into detail or if anything went wrong. I’m not sure even staggered startup would help enough for that as there’s only so much that can stretch things.
Thank you for your clarity on this. There’s a lot more information on other parts of the building process available, but amperage concerns at specific voltages and best practices for powering drives has less firm information out there, especially for those not using backplanes.
Incidentally, your account on the new forum was created last year, but I found a thread with you replying (last post in thread) on a similar topic I read before writing this on the old forum with a join date of 2016 listed. Kudos on that.
The key is that the case uses 6x 4 drive back planes. Each taking a molex connector.
The backplanes are simple affairs. They each support 4 drives, they’re just passive breakout backplanes, with hotswap, take one SFF-8087 connector, and a 4 pin molex connector. My PSU was big enough, and came with 3 sets of molex peripheral cables, so I ran all 3 to the backplanes. 2 backplanes per cable. Connected on the earliest connectors on the cable. This distributes the load best.
I looked at the preowned price of this system and, frankly I could have built a more expandable system cheaper if I had known about this in the planning stage and was more open to a server rack in the living room.
I appreciate your post.
Also, it seems like Stux used backplanes, which is understandable now that I’ve become more familiar with things following the research phase but is slightly disappointing for my purposes as it means a lot of SATA cables crammed in.
When selecting my case I used this build post as part of the research phase, but what I have ended up being somewhat different. Reddit - Dive into anything
If you need a laugh, here’s a picture of me putting the motherboard into the case for the first time. I followed the cooler’s user guide so closely that I messed up the orientation of the build’s CPU cooler for how I wanted it. In fairness, it was abstract pictures, minimal Engrish and did skip at least two steps (including removing the adhesive peel on the bracket holder and how to attach the wire frames to the fans). I suppose builders are just supposed to intuit everything not said as following the guide exactly like a first-time builder likely would have would turn out much like the below image, or worse, with the adhesive holding the mount not actually being sticky and the fans potentially having trouble holding on right above the CPU. Good manuals are nice, even generic ones.
