PSU capacity

This is a psu cable question

I have this power supply in my unRAID server.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341017

Other than the main bunch of cables that run the MB, there are 6 modular cables that can be plugged in.

2 of these are PCI express power cables that I don't need.

The other 4 are for HD's and fans and are currently being used.

My Antec 1200 case has space for 12 HD's, currently using 9. 

The case has a large fan at the top, two fans on the back, and there are 4 drive cage fans.  The fans all have moles power plugs.

The Biostar board has a molex fan plug on board and i have the two rear fans plugged into it (piggybacked). 

2 of the PSU HD cables each have 3 Sata plugs, and they are running 6 drives.

Each of the other two have 2 molex power plugs.  Each of them has one splitter on one molex plug making two Sata power ports and the other plug is used for fans (two piggybacked on each plug).  I have been trying to keep usage balanced.

So where I stand currently is I have one unused Sata plug (off one of the splitter).  All the fans are running except the one drive cage that isn't being used. 

I will soon be adding a drive which means I will use the last open plug the way it's currently configured.  I also need to add the last cage fan to one of the Peggy backed groups, but that will leave me where eventually I will have a problem with the last two drive slots.

So how much can you run off one cable?  I have run one of those online psu calculators and it shows that I have enough capacity (more than), just don't have enough plugs.  Do they make adapter cables to turn the pic express power plugs into Sata plugs?  Another option is to put 5 of the fans together on one of the Molex plugs, then I would have one left to use a splitter making the last two Sata powers.  5 fans seems like a lot to piggy back though.

This is a psu cable question

I have this power supply in my unRAID server.

 

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341017

 

Other than the main bunch of cables that run the MB, there are 6 modular cables that can be plugged in.

2 of these are PCI express power cables that I don't need.

The other 4 are for HD's and fans and are currently being used.

 

My Antec 1200 case has space for 12 HD's, currently using 9. 

The case has a large fan at the top, two fans on the back, and there are 4 drive cage fans.  The fans all have moles power plugs.

The Biostar board has a molex fan plug on board and i have the two rear fans plugged into it (piggybacked). 

 

2 of the PSU HD cables each have 3 Sata plugs, and they are running 6 drives.

Each of the other two have 2 molex power plugs.  Each of them has one splitter on one molex plug making two Sata power ports and the other plug is used for fans (two piggybacked on each plug).  I have been trying to keep usage balanced.

 

So where I stand currently is I have one unused Sata plug (off one of the splitter).  All the fans are running except the one drive cage that isn't being used. 

 

I will soon be adding a drive which means I will use the last open plug the way it's currently configured.  I also need to add the last cage fan to one of the Peggy backed groups, but that will leave me where eventually I will have a problem with the last two drive slots.

 

So how much can you run off one cable?  I have run one of those online psu calculators and it shows that I have enough capacity (more than), just don't have enough plugs.  Do they make adapter cables to turn the pic express power plugs into Sata plugs?  Another option is to put 5 of the fans together on one of the Molex plugs, then I would have one left to use a splitter making the last two Sata powers.  5 fans seems like a lot to piggy back though.

You have a two rail power supply.  One 12Volt (12V1) rail is used for two CPU power connectors.

The other (12V2) for everything else.    You can see how the cabling is wired here

http://www.ocztechnology.com/manuals/psu/OCZMXSP500-700.pdf

You have 25Amps available on that rail with at max 25x12 watts available. 300 Watts.  (Your on-line calculator probably is misleading you.  You have probably 250 watts available for disks)

On this page OCZ recommends, at max, 5 hard disks, but that is with a mid power graphics card.

Figure 5 amps for the motherboard and fans, 20 amps remain for disks.  At 3 Amps per non-green disk, that is 6 disks.  If you have some "green" drives, you can power a few more disks...

Unfortunately, you are probably at (or beyond) the capacity of that supply.

It is not an issue of what splitters you should use... but if you should use that supply to continue your expansion of your server.

Joe L.

At 3 Amps per non-green disk, that is 6 disks.  If you have some "green" drives, you can power a few more disks...

I imagine that this is talked about elsewhere, but thought I'd ask as I see the "3 Amp per disk" thing everywhere but don't get the math behind it.

From all my research, 3 Amp = 36W, and the WD site for Black drives states they use 10.7W under load.  So really, 200W 12v rail should handle 18 drives... well, in theory, so you back that off a bit to account for efficiency losses of 20-30% and you still get 140W or almost 13 drives.

If the 3 Amp "rule" is just to account for high drain of a motor when it first starts (moving from sleep to powered), wouldn't a staggered start help increase the drive count possible for a psu?  Also, why don't the hard drive manufactures list that requirement (start-up power draw)?

At 3 Amps per non-green disk, that is 6 disks.  If you have some "green" drives, you can power a few more disks...

If the 3 Amp "rule" is just to account for high drain of a motor when it first starts (moving from sleep to powered), wouldn't a staggered start help increase the drive count possible for a psu?  Also, why don't the hard drive manufactures list that requirement (start-up power draw)?

unRAID will spin up all the drive simultaneous when you first power up the server and will do the same if a read error occurs and it needs to spin up all the drives to re-construct what could not be read from the un-readable drive.    In the same way, a parity check will simultaneously spin up all the drives.

The staggered spin-up will work on those servers that do not spin down drives.  (but that is not unRAID)

The drive manufacturers don't advertise their worst statistics...  The marketing folks want you to thing they are "low power" all the time.

Unfortunately, if you exceed the power capacity of the supply when disks all spin up at the same time, you'll find random errors and disks going off-line, as they do not spin up reliably.   

When investigating the power draw of disks you need to concern yourself with their peak current draw on spin-up.  Unfortunately, WD does not make this easy for the Black drives.  They do not list the peak 12V current draw peak requirement as they do on the other drives they sell.  They only list the average.  (probably did not want to scare you.  only way to spin up faster is to draw more current.  Can't cheat physics.)

Joe L.

Basicaly,

 

You have a two rail power supply.  One 12Volt (12V1) rail is used for two CPU power connectors.

The other (12V2) for everything else.    You can see how the cabling is wired here

http://www.ocztechnology.com/manuals/psu/OCZMXSP500-700.pdf

 

You have 25Amps available on that rail with at max 25x12 watts available. 300 Watts.  (Your on-line calculator probably is misleading you.  You have probably 250 watts available for disks)

 

On this page OCZ recommends, at max, 5 hard disks, but that is with a mid power graphics card.

 

Figure 5 amps for the motherboard and fans, 20 amps remain for disks.  At 3 Amps per non-green disk, that is 6 disks.  If you have some "green" drives, you can power a few more disks...

 

Unfortunately, you are probably at (or beyond) the capacity of that supply.

 

It is not an issue of what splitters you should use... but if you should use that supply to continue your expansion of your server.

 

Joe L.

Thanks for this.  I started digging on this so I would understand what to look for if I'm going to have to replace this PSU.  I see the wiring diagram you sent, but I don't see where that refers to the number of rails or capacity of each rail. 

I did however, come across this on OCZ's website.

http://www.ocztechnology.com/images/awards/mxsp_wattage_charts.jpg

I think i'm seeing what to look for next time I shop for one of these.  What are the other columns for though?  What are the 5v and 3.3v lines for?  There is another 150W available there (at the wrong Voltage for drives).  More curiosity than anything else, just wondering what its used for. 

I have been noticing it seems like it seems like it takes a while for drives to spin up when I'm trying to watch a movie.  Maybe its the initial draw making it start up slow.  I haven't had any errors and figured it was just slow spin up on green drives.  Other than that everything functions correctly.

OK, now i'm seeing the whole single rails / double rail difference.  If it's a single rail design you aren't limited to half the capacity to run peripherals/drives. 

On a single rail design, how many amps do I need to allow for the MB to know what is left for drives?  If a non green drive is 3 amps, what do I allow for green drives since my final server will have 4 non green and 8 green drives?  at 2.5 amps for green drives that would be a total of 32 amps on drives.  Do I really need 25 amps for the MB??  I'm trying to figure out if I need to go to a 750-800 W PSU on a single rail design or if a 600-650W works.

Thanks.

At 3 Amps per non-green disk, that is 6 disks.  If you have some "green" drives, you can power a few more disks...

If the 3 Amp "rule" is just to account for high drain of a motor when it first starts (moving from sleep to powered), wouldn't a staggered start help increase the drive count possible for a psu?  Also, why don't the hard drive manufactures list that requirement (start-up power draw)?

It is exactly that.  When initially spinning up the current draw is much higher that once spinning.

The 3amp per drive is a rule that isn't really a rule, but it's a no brainer safety margin that was talked about then became a rule.

The reasons are as Joe mentioned. startup from spin down to spin up provides a significant surge on the PSU.  However this rule is not all that accurate.  From what I've read, peak power published specs are around 2A per drive, 1.5A to 1.75A for green drives.

I've generally spec'ed my machines with taking the 12v rail amperage, dividing by 2, then subtracting a drive.

To be on the safe side you could go with 3a per disk and have very little issues.

As far as 5 fans on one rail, I've done this without issues in the past, but you should review how many amps the fans are using. Also see if you can put some of them on the motherboard headers (providing they do not pull too much amperage). that will spread the load among the rails.

You cannot use the PCIe connectors for hard drives since they do not have 5v supply.

You may be able to use them for the fans with an adapter.

OK, now i'm seeing the whole single rails / double rail difference.  If it's a single rail design you aren't limited to half the capacity to run peripherals/drives. 

 

On a single rail design, how many amps do I need to allow for the MB to know what is left for drives?  If a non green drive is 3 amps, what do I allow for green drives since my final server will have 4 non green and 8 green drives?  at 2.5 amps for green drives that would be a total of 32 amps on drives.  Do I really need 25 amps for the MB??  I'm trying to figure out if I need to go to a 750-800 W PSU on a single rail design or if a 600-650W works.

 

Thanks.

That particular case can support up to 20 disks with the correct 5x3's.

I would get a PSU with at least 60a on the 12v rail. I think the Corsair 750s reach that.

Mind you, I have a corsair 620hx with 3 12v rails and I have 17 drives, 3 controllers, 8gb of ram 4 5x3's with fans and back plane, 5 7200rpm drives, 12 5400rpm drives. I do not have any issues.

But this particular corsair somehow allows sharing power from the other rails.

The corsair 650w is one that limetech used in its systems with a 15 drive capacity. So that should work for you. They have 52A single rail.

Sent from my SGH-I727R using Tapatalk

Been looking at PSU's and thought I'd bounce a couple off the crowd.

I have had two OCZ PSU's.  They are 2 and 4 years old now, and both have been quiet and trouble free.  I was going to start there:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341051: $85 after rebate, 650W, 54 amp rail, 85% Eff, 9 Sata ports.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341052: $95 after rebate, 750W, 62 amp rail, 85% Eff, 9 Sata ports.  The only problem with this one is a seemingly high number of people complaining it's loud under load.  (big issue for me).

Then I started looking at others and the only one that feel into the price/options catagory is Corsair, which seems to be favored around here.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139012: $89 after rebates and promotions, 650W, 52 amp rail, 85% eff, 9 Sata ports

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139021: $89 after mail in rebate, 750W, 62 amp rail, 85% eff, 8 Sata ports

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139012: $129 after mail in rebate + $6 shipping, 750W, 60 amp rail, 90% eff, 12 Sata ports.  A couple nice perks on this one with efficiency and extra Satas out of the box, but not sure its worth the $$

So the question is am I missing anything.  Is Corsair better than OCZ?  Am I missing any pros/cons in these options?

Is the corsair $129 psu the one with the modular cables and 12 sata power cables?

How many modular power cables?

At the very least this PSU provides 12 sata connectors for the 12 slots in your case.

It's modular so you can leave out cables that are not used. You know right from the get go, It's designed for 12 sata drives.

I would lean on this one. Also if you start to upgrade to 5x3's to hold your drives, It should handle the upgrades. 

My Corsair 620 with 3 12v 18a rails handles 18 drives.

I have the last one you listed (which links to a 650w modular)  and love it. Ive had 12 drives running on it without issue.

If you want to be extra safe go with the 750W Version, but likely wont need that much.

Sent from my SGH-I727R using Tapatalk

I fixed the 3rd Corsair link above.  The link was a duplicate of one of the others.  Copy / Paste error. 

Is the corsair $129 psu the one with the modular cables and 12 sata power cables?

 

How many modular power cables?

 

At the very least this PSU provides 12 sata connectors for the 12 slots in your case.

It's modular so you can leave out cables that are not used. You know right from the get go, It's designed for 12 sata drives.

 

I would lean on this one. Also if you start to upgrade to 5x3's to hold your drives, It should handle the upgrades. 

 

My Corsair 620 with 3 12v 18a rails handles 18 drives.

No, I had a bad link there.  The one with 12 sata connectors is more expensive.  See it now.

I looked up your 620 and it's not available anymore (at least at newegg).  I'm feeling like any of the 650 supplies above will work for me up to 12 drives, so it would just come down to which one is better / quieter.

The more expensive 750 just requires less adapters with 12 connectors, and is a 90% efficient PSU.  As noted it also gets me down the road if I start swapping out for 5x3 cages, and expanding down the road.  I'm don't have a good feel for when I will have need for that much space though.  With 12 TB of usable space now, I'm 55-60% full.  I get to 18 TB without expanding cages or even going up to 3 TB drives so I assume it will be a while.

I purchased the 620 because that was available then.

If I were in your position, I would be purchasing the modular 750.

You'll do fine with the 650's you posted.

However for me, Not having all those extra cables in a machine, plus power to spare with a growth potential of 20 drives would sell me on the 750. Especially knowing the PSU is designed for many peripherals right from the get go.

Later on if you decide to go with 5x3's you may be able to get new molex cables from Corsair to swap for the sata power cables.

That was another reason I went modular.

If you go with another psu, remember to factor in the cost of splitters or adapters + shipping.

Oh.. and it's only because your case has the potential for 20 drives, otherwise I would go for the 650's if the case only could support 15 drives or so.

I purchased the 620 because that was available then.

If I were in your position, I would be purchasing the modular 750.

 

You'll do fine with the 650's you posted.

 

However for me, Not having all those extra cables in a machine, plus power to spare with a growth potential of 20 drives would sell me on the 750. Especially knowing the PSU is designed for many peripherals right from the get go.

 

Later on if you decide to go with 5x3's you may be able to get new molex cables from Corsair to swap for the sata power cables.

 

That was another reason I went modular.

 

If you go with another psu, remember to factor in the cost of splitters or adapters + shipping.

 

Oh.. and it's only because your case has the potential for 20 drives, otherwise I would go for the 650's if the case only could support 15 drives or so.

Thanks for the advice.  Pretty sure all of the above are fully modular.  Agree on not having all those extra cables taking up space.  I will order something in the next day.  One of those has a promo that ends on the 8th so will decide by then.