Power supply requirement for 5in3 backplanes?

[PeterB]

I'm in the position of having to purchase another psu and my plan is to obtain a more suitable unit for mu unRAID server, and redeploy the HEC Raptor 500.

 

Looking at photos and specifications of 5in3 backplanes, it appears that they have 2, or even 3, power connectors.  My question is whether it is necessary to make a connection to both (or all three)?

 

My choice of power supply is currently being limited by the desire to provide as many 4 pin molex connectors as possible (reducing the possible need for 'Y' doublers).

 

My current list of potential choices (in order of preference) is:

1) Seasonic X650

2) Thermaltake ToughPower Grand 650

3) Corsair HX650

 

These all come with a maximum of eight 4-pin Molex.  I note that some newer models (eg Seasonic x560 and x660 have reduced to 5 4-pin molex).

[furymaster]

It is not required, but suggested. It has to do with the maximum ampere of the molexes. You should not use Y cables to make contact to both power connectors, as this would overuse the single molex plug where thy Y cable is plugged in.

 

I have a SilverStone OP750W, which has 12 molex plugs - enough for quite a lot of cages.

 

Hope you'll find a PSU which has enough molexes - it shoud be single rail 12V too!

[ohlwiler]

I read somewhere here of someone requesting additional molex cables from Seasonic. They were sent for free in a very timely fashion.

[PeterB]

I read somewhere here of someone requesting additional molex cables from Seasonic. They were sent for free in a very timely fashion.

 

That would be ideal ... but I wonder whether they would be prepared to send them internationally - to the Philippines?

[lionelhutz]

One molex should power a whole cage. However, it's not a bad idea to run 2 seperate cables to 2 different plugs to make sure the power is solid.

 

Each pin on a SATA power connector can handle 1.5A and there are 3 of each voltage in the connector. So, a SATA can handle 4.5A. 2 SATA would power 5 drives but it could be marginal on initial drive spin-up. 3 SATA would definately be safer.

 

Peter

[SSD]

I've run 10 green drives off of one molex connector for well over a year. The connector didn't even get warm.  I think sometimes the specifications are extremely conservative.  (I did use the beefiest molex I could find with the lowest gauge wire).

 

I am not convinced that every 5 in 3 is wired to share the power inputs.  I remember a post where someone said they took one apart and found 1 molex powering 2 drives, a second molex powering another 2, and the third molex powering one drive plus the electronics and fan.  They easiest way to know for sure is to try it with only plugging in one molex and see if all of the ports work. 

 

My personal opinion is running one 5 in 3 off of one molex would not be a problem.  You could even do two (again this is my opinion), but why would you want to?

[Rajahal]

It is not required, but suggested. It has to do with the maximum ampere of the molexes. You should not use Y cables to make contact to both power connectors, as this would overuse the single molex plug where thy Y cable is plugged in.

 

Do you say that from experience, or do you have some source for that info?  That's basically the exact opposite of my experience.  First off, every 5-in-3 cage I've used requires all power ports to be populated.  Generally one port will power three drives, and the other will power the remaining two drives and the fan.  I have seen one 5-in-3 with three power ports that was split up as two drives per port, then the third port had one drive and the fan.  I've never seen a 5-in-3 that can be powered completely with just a single port.

 

Secondly, I use Y style molex splitters in nearly all of my builds.  I've never had an issue with using a single molex splitter to power a drive cage with two power ports.  As long as you are using a PSU with a strong single +12V rail, you shouldn't have any issues.

[furymaster]

As far as I have seen, my new Supermicro cages have connected power supplies. I don't put my hands into fire for it's been a few weeks since I put them in my server.

 

As far as my electronic knowledge reaches, the usage of Y-cables should be avoided. Every plug has resistance, and every connection leads to voltage loss. It might be minor, and the usage practically, but I had very bad experiences with those connectors some years ago. The problem occured long time after installing the machine, the Y-plug was the reason for two hard drives to fail...

 

That's why I avoid them and keep buying PSUs which do have enough molex plugs. Using modular PSUs gives you more flexibility and sure enough molex plugs.

[opentoe]

The double connectors, do you mean these guys?

 

[furymaster]

Yes, that's an molex Y-cable. I personally avoid them where I can

[PeterB]

In 30 years of professional experience, I have seen a molex connector go bad once.  It was, obviously, making poor contact, had overheated badly and destroyed the nylon shell.  I don't believe that the problem is restricted to Y splitters.

 

The materials used in the contacts are not the best and oxidation can occur if the contact is not tight.  One thing which might help is to apply a little contact lubricant before mating the connectors.  If contact lubricant is not available, petroleum jelly can be used (sparingly).