Hello,

 

Without doing my homework, I did purchase http://www.newegg.com/Product/Product.aspx?Item=N82E16817341022 

I should have ordered a single rail one. I am building a budget system (total maximum: 12 drives) with Intel E3400 processor (65W). All the drives I will be using will be 5400/5900RPM green drives. The above power supply's spec says: output: +3.3V@25A, +5V@25A, +12V1@25A, +12V2@25A, [email protected], [email protected]

Do you guys think I would be good with this power supply? I hate to do RMA. Please advice. Thanks...

I also ordered one of those for my new build:

 

http://lime-technology.com/forum/index.php?topic=12117.msg115294#msg115294

 

My case will only go to max 8 drives though.

Thanks, I want to make sure if it would support 12 green drives. Anyone, any thoughts please?

12 green drives would be pushing it because of the split rail.  Frankly, I would not go over 10.

Hello,

 

Without doing my homework, I did purchase http://www.newegg.com/Product/Product.aspx?Item=N82E16817341022 

I should have ordered a single rail one. I am building a budget system (total maximum: 12 drives) with Intel E3400 processor (65W). All the drives I will be using will be 5400/5900RPM green drives. The above power supply's spec says: output: +3.3V@25A, +5V@25A, +12V1@25A, +12V2@25A, [email protected], [email protected]

Do you guys think I would be good with this power supply? I hate to do RMA. Please advice. Thanks...

Basically, you have 1 25 amp rail available for disks, and it probably shares that rail with the motherboard.   You'll probably be pushing it once you get past 10 drives.

 

If you know how to solder, you can construct a custom cable that grabs the needed 5 volts from one of the IDE connectors and the 12 volts from one of the PCIe connectors designed for power hungry video cards.  With a custom cable you can easily power the 12 drives by using the normally unusable second 12 volt rail.  (Just be VERY careful you have the right voltages on the right pins... otherwise, crispy drive electronics follow shortly)

 

Joe L.

I got an 650 watt OCZ power supply for almost free with a combo deal at Newegg. It too claimed to have separate 12 volt rails. I opened it up to double check and all the 12 volt leads were soldered to the same circuit board pad. I suspect yours is the same, but the only way to know for sure is to take it apart and look.

Without doing my homework, I did purchase http://www.newegg.com/Product/Product.aspx?Item=N82E16817341022 

I should have ordered a single rail one. I am building a budget system (total maximum: 12 drives) with Intel E3400 processor (65W). All the drives I will be using will be 5400/5900RPM green drives.

 

If you work with a ball-park figure of 2A spinup current for a 'green' drive, you can see that you will be straining that psu, even before you consider any other load on the same rail - (12*2 = 24A).  Unfortunately, that unit claims to comply with the ATX12V v2.2 specification, which demands separate 12V rails with individual over-current protection.  However, some manufacturers cheated and did connect all the 12V rails internally.  If you can confirm whether that is the case with this model, or you can reallocate the loads by moving connections internally, then you may be okay.

 

 

The above power supply's spec says: output: +3.3V@25A, +5V@25A, +12V1@25A, +12V2@25A, [email protected], [email protected]

 

Be careful - the unit is rated at 550W, but if you attempt to draw the maximum current, as specified, from each rail, you will be running at (ignoring the 5VSB) (3.3*25)+(5*25)+(12*25)+(12*25)+(12*.3) = 811W, clearly far in excess of the maximum rated total load.  I do wonder whether, in their efforts to 'cheat' the v2.2 spec, manufacturers commoned the 12V rails and set a current limit which matched that of just one rail.  In other words, there are two 12V rails, each of which can supply 25A, but for which the maximum combined load is still only 25A.

I like to be safe and figure 2.5amps for each green drive. I'm only missing a PSU for my build now, but there aren't any budget PSU's that supply 40A on a single rial with active PFC that I feel confident buying at this time.

here's an interesting thread;

 

http://lime-technology.com/forum/index.php?topic=11799.0

 

It seems you need about 0.6A per WD Green drive. Much less than the 2A typically listed. Even being conservative and allowing 1A per drive means 12 WD green drives is possible.

 

Peter

here's an interesting thread;

 

http://lime-technology.com/forum/index.php?topic=11799.0

 

It seems you need about 0.6A per WD Green drive. Much less than the 2A typically listed. Even being conservative and allowing 1A per drive means 12 WD green drives is possible.

 

Peter

 

Personally, I would rather not rely on someone else's measurements - they may be right some of the time, but we have no idea of the test conditions. 

 

WDC give there figures here - http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-701229.pdf

 

These are quite a lot higher.  They may not always be seen in use, but these would be a safer bet if budgeting for a power supply.

WDC give there figures here - http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-701229.pdf

 

These are quite a lot higher.

 

.. and even then, the spec sheet doesn't state whether that value relates to the optional 'low start' setting, or the standard, default, setting.

 

They may not always be seen in use, but these would be a safer bet if budgeting for a power supply.

 

Indeed - far safer to have an extra few amps capacity, than to risk your system shutting down or worse, producing random errors, every time you have a multiple drive spinup situation.

WDC give there figures here - http://www.wdc.com/wdproducts/library/SpecSheet/ENG/2879-701229.pdf

 

These are quite a lot higher.

 

.. and even then, the spec sheet doesn't state whether that value relates to the optional 'low start' setting, or the standard, default, setting.

 

From what I have read, this would be standard - as I read it, the low-start setting lowers current down to about one amp peak.

I shall open the case and post some pictures this evening once I get home. Thanks all for the input.

1.55A per WD Green leaves 76.8W extra on the 12V rail for the motherboard and controllers.

 

Peter

I noticed that the ouputs are soldered to a circuit inside and so I could not tell if they are branched off from same line or each rail is seperate. Anyways, I decided to use it. Currently I plan on using 4 disks only. I was thinking if I can use the output provided for Graphics card (if monoprice sells an molex adapter) to power additional drives (once I cross 10).

 

Thanks everyone for your comments and opinion.

Anyways, I decided to use it. Currently I plan on using 4 disks only.

 

That's fair enough.  I built my unRAID box with a 500W multi-rail PSU initially.  I've only recently upgraded the psu in preparation for array expansion.

 

I was thinking if I can use the output provided for Graphics card (if monoprice sells an molex adapter) to power additional drives (once I cross 10).

 

Can you find a specification for which connections come from which internal rail?  It seems quite likely, but do you know for sure that the graphics card 12V is connected a different rail from the disk connectors?

The company website provides a "mechanical drawing", but since it is not a circuit diagram I don't know if it tells us anything relevant to this discussion.

 

http://www.ocztechnology.com/res_old/manuals/psu/OCZ550FTY.pdf

 

 

The company website provides a "mechanical drawing", but since it is not a circuit diagram I don't know if it tells us anything relevant to this discussion.

 

It does, yes!

 

It shows that the 12V supplied to the video connectors comes from the same rail as the 12V supplied to the disk drive connectors.

 

Rail 1 supplies the mobo and cpu connectors.  Rail 2 supplies the rest.  So, if the original poster wants to spread the load from his disk drives across the two rails, he will have to take the alternate 12V from mobo or cpu connectors.

The company website provides a "mechanical drawing", but since it is not a circuit diagram I don't know if it tells us anything relevant to this discussion.

 

It does, yes!

 

It shows that the 12V supplied to the video connectors comes from the same rail as the 12V supplied to the disk drive connectors.

 

Rail 1 supplies the mobo and cpu connectors.  Rail 2 supplies the rest.  So, if the original poster wants to spread the load from his disk drives across the two rails, he will have to take the alternate 12V from mobo or cpu connectors.

Exactly.    He'll need a custom made cable to tap into those.  if it were me, I'd use a motherboard extender cable and splice into it a standard molex/sata splitter.  Then there is no need to do anything but put the extender cable in-line with the 24 pin motherboard connector and use the additional capacity from the spliced in molex/sata splitter. ( Since you need the 5Volt line, it is an easier cable to make than one using the CPU power connectors.  They do not have 5Volts on them)

Sure, he could start modifying the wiring, but if he's got a dedicated 25A for only the HDD's then he should be able to run 12 WD green from it as is (assuming the 12v2 can supply the 25A it is specified as capable of supplying).

 

Peter

Sure, he could start modifying the wiring, but if he's got a dedicated 25A for only the HDD's then he should be able to run 12 WD green from it as is (assuming the 12v2 can supply the 25A it is specified as capable of supplying).

 

Peter

Very true, I was not thinking about that.  On a different multi-rail OCZ supply I own, the 12V rail that feeds the Motherboard is the same one that feeds all the disks, so I don't have exclusive use of it. (It also means I cannot use the same technique of splicing into an extender cable, since it is not a different rail than the one powering the disks)