# What kind of PSU wattage do I need for 10 HDDs?



## AshleyAshes (Oct 6, 2011)

So, I have an HTPC sitting here, built out of an old Athlon 64 3200+ and I added the second 2TB drive to it last night.  My intention is to keep adding drives to it when it gets full until the case is maxed out at 9 HDDs, or 10 if I remove the optical drive.

Then comes the issue of the PSU.  The Orion 585w PSU in this thing is kinda loud, at least for what you'd want from a movie machine, and it only has two SATA power connectors on it.  I realize I could get Molex+SATA adaptors easily, but I'd like to replace it with a quieter and more reliable PSU for the long term.

So the question is, how many watts do I really need to power an Athlon 64 3200, Radeon HD 4650, and 9 or 10 hard drives?

My main desktop has a Corsair Builder Series 600w unit in it, I like it's level of sound output, and it's much quieter than the Orion in the HTPC.  The same PSU comes in 500w and 430w flavors, which are cheaper.  I'd like to not spend more than I have to, and have watts to spare.  Even if I upgrade this box, it'll never be more than an HTPC so I doubt it'll ever see a CPU rated at over 35w TDP.  I figure any PSU for this could migrate along into a replacement HTPC build on a more modern low end CPU.
Any ideas?


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## ToeClaws (Oct 6, 2011)

The average power required by a hard drive is around 30W to spin up, and 20w during normal operation.  When idle (but on), they drop to single watts.  Now... where this varies is hard drive type and performance.  Green hard drives will draw less (but are slow), performance beasts take a lot more, so you'll have to inventory what you have.  I'm also using standard 3.5" type drives here.

So if you want to build something that can handle 10 drives assuming the 30W average, that's 300W for spin up, 200 for operation (yay for easy 10x multiples) just for the hard drives.  Green drives or 2.5" drives would drop it considerably.


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## AshleyAshes (Oct 6, 2011)

ToeClaws said:


> The average power required by a hard drive is around 30W to spin up, and 20w during normal operation.  When idle (but on), they drop to single watts.  Now... where this varies is hard drive type and performance.  Green hard drives will draw less (but are slow), performance beasts take a lot more, so you'll have to inventory what you have.  I'm also using standard 3.5" type drives here.
> 
> So if you want to build something that can handle 10 drives assuming the 30W average, that's 300W for spin up, 200 for operation (yay for easy 10x multiples) just for the hard drives.  Green drives or 2.5" drives would drop it considerably.



Right now it's a pair of Seagate Green drives, mainly because they're the cheapest and largerst I can get.  However, I've read that Green drives are more expensive to produce than they should be and the idea could be abandoned.  Right now my plan is to just toss in HDDs on demand, since drives keep getting bigger and cheaper, it makes no sense to buy them all at once.  So I can't say with any accuracy what I'll be installing 6 months from now when it's time to add another drive, or the six months after that, or after that.


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## FF_CCSa1F (Oct 6, 2011)

I'm sorry, but assuming 20W for consumer hard drive during normal operation is extremely excessive; 20 and 30W are both only close to the absolute maximum power consumption you'll see when the drive spins up. Using the Seagate Barracuda 7200.12 series for reference, the quoted power consumption for typical usage is 6.57W, and the maximum power consumption during spin-up is 24W.

While the six-and-a-half Watt figure might sound somewhat optimistic, they have actually quoted quite pessimistic testing conditions. If one were to use the disk to the brim of its capabilities, it still wouldn't even be close to 10W. That number is, however, not what matters here, as you're still going to need to spin the disks up all at once. 30W per disk is indeed a quite reasonable figure for that, keeping in mind that it includes a fair amount of headroom.

I'd consider a Seasonic S12II-380W or 430W unit if I were in this position. They're very nice units for their price.


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## AshleyAshes (Oct 6, 2011)

FF_CCSa1F said:


> I'm sorry, but assuming 20W for consumer hard drive during normal operation is extremely excessive; 20 and 30W are both only close to the absolute maximum power consumption you'll see when the drive spins up. Using the Seagate Barracuda 7200.12 series for reference, the quoted power consumption for typical usage is 6.57W, and the maximum power consumption during spin-up is 24W.
> 
> While the six-and-a-half Watt figure might sound somewhat optimistic, they have actually quoted quite pessimistic testing conditions. If one were to use the disk to the brim of its capabilities, it still wouldn't even be close to 10W. That number is, however, not what matters here, as you're still going to need to spin the disks up all at once. 30W per disk is indeed a quite reasonable figure for that, keeping in mind that it includes a fair amount of headroom.
> 
> I'd consider a Seasonic S12II-380W or 430W unit if I were in this position. They're very nice units for their price.



But isn't spinup wattage the most inportant value in this question, since when you press the power button, all the drives spinup simultaniously?


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## FF_CCSa1F (Oct 7, 2011)

AshleyAshes said:


> But isn't spinup wattage the most inportant value in this question, since when you press the power button, all the drives spinup simultaniously?



That depends. The 20-ish Watt a drive will draw is only for a very limited time. A high-quality power supply rated for less than 200W on the 12V rail will have no problems spinning ten disks up while the computer starts, but it is pushing the boundaries of reliability a bit. That's why I'd recommend the 380 or 430W versions of the Seasonic S12II, even though there is a 330W model available.


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## Aden (Oct 7, 2011)

AshleyAshes said:


> But isn't spinup wattage the most inportant value in this question, since when you press the power button, all the drives spinup simultaniously?



Not only that, but you want to be generous with your estimates anyway. Better to have and not need than vice-versa.


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## ToeClaws (Oct 7, 2011)

I agree, 20W is pretty excessive, but I'm shooting high rather than low for general power consumption.  That low wattage will vary a lot if the drive is being worked harder.  Besides, spin-up power is the important one.  Yes, it's only used for a short time, BUT, if your power supply can't surge to that point, you're going to have a problem.  Also, there are times when you can't avoid simultaneous spin-up, such as system start or resuming from suspend.  

Also, powers supplies aren't really all that expensive - it's safer/better to go with a big one and know you have the extra juice than aim low and regret it.


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## Runefox (Oct 7, 2011)

Yeah, echoing the sentiment that spin-up power usage is the most important number. It's the maximum, and it's ALWAYS going to happen, *all at once*. If there's not enough peak wattage to facilitate the startup, then you're not going to reliably get past POST. That said, let's add it up and see what the worst-case scenario might be.

Assuming the high end of 10x30W for spinup, you're looking at 300W for the HDD's. TDP for the 3200+ is 89W (closer to 40W with Cool & Quiet enabled), the HD 4650 gains about 60W at load on top of what I imagine is about 20W at idle for a total of say 80W. Optical drives don't really count unless they're running full-tilt, at which point you're looking at maybe 15W, and the rest of the computer (on that old beat-up motherboard) probably doesn't draw any more than 30W itself on the HIGH end (probably closer to 15-20W for this). Adding that up, at absolute peak (which is almost an impossibility), you're looking at *514W*. You'd have to be playing back full 1080p video with mocomp while burning a DVD and doing Prime95 with all the disks spun down, then suddenly have them all spin up at once to hit that mark.

... Sooooo, even in a nightmare scenario, a decent 500W peak supply should be able to handle that. Do note "peak"; That could also mean a 350W continuous if the supply is good (and as far as continuous power goes, that's about all it'd need).


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## Draconas (Oct 8, 2011)

from the others posts, shoot for a 600watt PSU just to be safe, and if you ever decide to go past 10 drives or, hell even get a better videocard if you really wanted.


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## AshleyAshes (Oct 8, 2011)

Draconas said:


> from the others posts, shoot for a 600watt PSU just to be safe, and if you ever decide to go past 10 drives or, hell even get a better videocard if you really wanted.



There will never be more than 10 drives, the case can't physically house more than 10 drives.  There won't be a 'better' video card, maybe a new one, but it'd always be the low end type since it's just an HTPC. All I need is a card to offer up DXVA.


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## CyberFoxx (Oct 8, 2011)

I say go for 600-watts. Always good to have too much, than too little.

My experience with finding a PSU for a drive-heavy setup:
I got an old Celeron D set up as a JBOD. Sure, the Celeron D series wasn't really known for being low power, and it has six semi-old PATA HDs (13GB, 2x20GB, 120GB, 160GB and 250GB) in it. But it's just using the Intel on-board video, and it's always in textmode anyway, so saving a bit of power there. 450-watts wasn't cutting it (Would start to boot, but then cutout half-way through kernel startup), and neither was a 500-watt PSU (HDs would spindown for power saving, then never come back). I ended up having to put in a Corsair 650-watt PSU I was able to get on sale. Haven't had a problem with it since.


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## Rex Aeterna (Oct 8, 2011)

watts specs can be meaningless on the PSU. it all depends on how much amps it can put out on a 12v rail to determine it's actual power excursion. for hard drives and nothing else you can easily get away with 430w psu but it's always good to have some headroom for future upgrades so i would go with something like 550w just incase you might want to add a low powered gpu or something. look at seasonic,corsair,antec or rosewill. they tend to be very well built and usually has more then enough amps for their actual wattage rating cause lot of psu's say 600w or something but in reality can barely even pull 400-450w cause the amp rating on the 12v rails.


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## FF_CCSa1F (Oct 8, 2011)

CyberFoxx said:


> I say go for 600-watts. Always good to have too much, than too little.



Assuming a decent-quality unit, 600W is ridiculously high.



Rex Aeterna said:


> watts specs can be meaningless on the PSU. it all depends on how much amps it can put out on a 12v rail to determine it's actual power excursion.



Not quite. The power rating of a power supply is derived from the current it can output, and units that quote made-up wattages are generally in such a low segment of the market that they aren't even worth considering. However, it is true that many ultra low-end units cannot provide the power that they claim to be able to, it just means that they aren't able to supply the current advertised either. 

Many other cheap (or old) units can actually provide the advertised power, but they're old designs that have a majority of their power nestled in the 5V rail. A 600W unit that can provide 100A on the 5V rail but only 8 on the 12V one is going to be quite useless in a modern computer.



Rex Aeterna said:


> [...] seasonic,corsair,antec or _rosewill_ [...]



One of these don't belong. While I'm sure Rosewill have some units built by decent OEMs, they don't by any means have the same sort of pedigree as Seasonic, Corsair or, to a lesser extent, Antec.


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## Runefox (Oct 9, 2011)

FF_CCSa1F said:


> Assuming a decent-quality unit, 600W is ridiculously high.


For the sake of argument, higher wattage supplies typically are more efficient than the lower-wattage variants for the money (you can definitely get some highly efficient low-wattage supplies, but you're going to pay a premium close to the higher capacity supplies for it).


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## FF_CCSa1F (Oct 10, 2011)

Runefox said:


> For the sake of argument, higher wattage supplies typically are more efficient than the lower-wattage variants for the money (you can definitely get some highly efficient low-wattage supplies, but you're going to pay a premium close to the higher capacity supplies for it).



Can you place a case to that point? I can't agree with that just like that. A higher-power unit of the same price as a lower-power one almost without exception will be a lower-quality one, and skimping on quality rarely translates to higher efficiency. Furthermore, in an application such as this, where the power is only needed for a brief moment during start-up, a high-power PSU is more likely to be running (further) below its point of maximum efficiency.


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## grimtotem (Oct 11, 2011)

why not jsut buy a 1k watt supply and be content.


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## AshleyAshes (Oct 11, 2011)

grimtotem said:


> why not jsut buy a 1k watt supply and be content.



Because it'd be expensive, absurdly overkill, well beyond what I'll ever need, loud and spew a lot of unneeded heat into my bedroom?


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## Aden (Oct 11, 2011)

AshleyAshes said:


> Because it'd be expensive, absurdly overkill, well beyond what I'll ever need, loud and spew a lot of unneeded heat into my bedroom?



though you are in canada so the heat might not be unwelcome


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## Sai_Wolf (Oct 11, 2011)

Modular power supplies are sexy. That is all.


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## AshleyAshes (Oct 11, 2011)

Aden said:


> though you are in canada so the heat might not be unwelcome



Not really.  I'm on the 11th floor, I never even turn the heat on in the winter because enough heat rises from lower apartments.  Actually, room temperature in winter is often around 23-24'C instead of 21 which I would prefer.  ...But then, I sleep with my window open in the winter...


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## FF_CCSa1F (Oct 13, 2011)

If your windows aren't frozen shut, it isn't really winter.


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## dietrc70 (Oct 14, 2011)

I thought Runefox had good advice.  If anything, 500W is on the high side, since any good PSU is designed to handle extra draw on bootup.  I suspect that a quality 350W-400W would be adequate

I'd like to add that PSU's usually reach peak efficiency at about 80% of their rated output.  They get less efficient when they have to supply loads much lower than they are designed to.

It's too bad that SATA controllers rarely support staggered spin up.  I used to build my PC's out of old 10K SCSI drives that sounded like small airplane turbines.  The Adaptec controller would spin them up one by one.  It sounded really cool.


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## AshleyAshes (Oct 14, 2011)

dietrc70 said:


> It's too bad that SATA controllers rarely support staggered spin up.  I used to build my PC's out of old 10K SCSI drives that sounded like small airplane turbines.  The Adaptec controller would spin them up one by one.  It sounded really cool.



Yeah, any SATA controller with staggered spinup would cost me far more than getting a PSU that can just deal with the high load at boot.  So I'm using cheap $20 4 port SATAI controllers instead.


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