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The Power Supply Thread

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A good PSU for unRaid has the following:

 

1. Single 12 volt rail.  A subsequent figures refer to the 12 volt rail.

2. The minimum capacity that can power your build. Any more will just waste power. All drives will be in use during startup, shutdown, parity check, parity build, failed drive emulation, and drive rebuild, but startup requires the most power.

3. 2 amps (24 watts) per green drive and 3 amps (36 watts) per non-green drive on the 12 volt rail.

4. 5 amps (60 watts) for the motherboard on the 12 volt rail.

 

 

Please make comments below and I will incorporate changes in to this post.

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Here's the top recommended manufacturers and models:

 

Seasonic

Undeniably the best, but also quite expensive.  Seasonic also manufacturers the internals of some of the models offered by several other major brands (Corsair and Antec specifically).

 

Modular:

 

SeaSonic X series SS-400FL 400W

- fanless

- Gold certified

- 33A, supports up to 15 green drives or 9 7200 rpm drives

- recommended for a small to medium sized server in which noise levels are a big concern

 

Seasonic SS-560KM 560W

- Gold certified

- 46A, supports up to 21 green drives or 13 7200 rpm drives

 

SeaSonic X Series X650 Gold 650W

- Gold certified

- 54A, supports up to 25 green drives or 16 7200 rpm drives

 

SeaSonic X Series X-850 850W

- Gold certified

- 70A, supports up to 33 green drives or 21 7200 rpm drives

- recommended for the big spender who wants to buy the most expensive power supply on this page

 

Non-modular:

 

Seasonic SS-850HT 850W

- Silver certified

- 70A, supports up to 33 green drives or 21 7200 rpm drives

- recommended for a 20 drive server using all 7200 rpm drives

 


 

Corsair

The best of the budget brands.

 

Modular:

 

CORSAIR HX Series CMPSU-650HX 650W

- Bronze certified

- 52A, supports up to 24 green drives or 15 7200 rpm drives

 

CORSAIR HX Series CMPSU-750HX 750W

- Silver certified

- 60A, supports up to 28 green drives or 18 7200 rpm drives

 

CORSAIR HX Series CMPSU-850HX 850W

- Silver certified

- 70A, supports up to 33 green drives or 21 7200 rpm drives

 

Non-modular:

 

CORSAIR Builder Series CX430 CMPSU-430CX 430W

- 28A, supports up to 12 green drives or 7 7200 rpm drives

- recommended for small servers, 10 drives or less

 

CORSAIR Builder Series CX500 (CMPSU-500CX) 500W

- 34A, supports up to 15 green drives or 9 7200 rpm drives

- recommended for medium servers, 10 - 15 drives

 

CORSAIR Enthusiast Series CMPSU-650TX 650W

- 52A, supports up to 24 green drives or 15 7200 rpm drives

- recommended for 20 - 24 drive servers using only green drives or medium sized 15 drive servers using only 7200 rpm drives

 

CORSAIR Enthusiast Series TX650 V2 650W

- Bronze certified

- 53A, supports up to 24 green drives or 15 7200 rpm drives

- recommended for 20 - 24 drive servers using only green drives or medium sized 15 drive servers using only 7200 rpm drives in which noise is a concern (as the variable fan speed will help the server stay quieter when under low load)

 


 

Antec Neo Eco

Rivals the Corsair PSUs, but often more expensive, and choices are limited.

 

Modular:

 

None

 

Non-modular:

 

- Plus certified

- doesn't come with a power cable

- 30A, supports up to 13 green drives or 8 7200 rpm drives

- recommended for smaller servers, 10 drives or less

 

Antec NEO ECO 520C 520W

- Plus certified

- doesn't come with a power cable

- 40A, supports up to 18 green drives or 11 7200 rpm drives

- recommended for mid-sized servers, 10 - 15 drives

 

Antec NEO ECO 620C 620W

- Plus certified

- doesn't come with a power cable

- 48A, supports up to 22 green drives or 14 7200 rpm drives

- recommended for larger servers, 10 - 22 drives

 

Antec just released a new 'High Current Gamer Series' of PSUs that should be a step up from the Neo Ecos, but they have not yet been tested with unRAID.

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Here's some discussion as to the pros and cons of different PSU features:

 

Why choose a modular PSU?

 

Modular PSUs allow you to use only the cables you need, and remove the rest.  This reduces cable clutter and can benefit airflow through the case.  Some companies that sell modular PSUs will also sell or give you extra cables of certain types.  This can be especially beneficial in the case of unRAID servers, as servers generally need a lot of one type of power connection (either SATA or molex).  These extra cables can reduce or negate your need for power splitters.

 

Modular PSUs are more important the smaller the server is.  A large case like a Norco 4224 has ample room for the bundle of unused cables that would accompany a non-modular PSU, but in a small case like the LIAN LI PC-Q08B space is at a premium.  Generally speaking, if you are building a small form factor (SFF) server, then you should seriously consider a modular PSU.

 

Why choose a non-modular PSU?

 

Because it saves you money.  Modular power supplies often cost around $50 more than their non-modular equivalents.  If you are building your server in a large case with plenty of room to store extra cables, then the benefits of a modular PSU are significantly mitigated.

 

Why choose a fanless PSU?

 

A fanless PSU is completely silent.  If you are building a silent server, then you will need to use a silent PSU.  Keep in mind that any fan noise in your server whatsoever will already likely be louder than any fan noise coming from a PSU, so unless you are building a completely fanless/silent server, then a fanless PSU probably isn't worth the extra expense.  A fanless PSU will also use up less power, but only marginally less.

 

Why choose a PSU with a variable fan speed?

 

A PSU with a variable fan speed can help minimize noise and power usage.  Some fan speeds are based on a temperature sensor, some are based on the load on the PSU.  Either way, when your server is sitting idle the fan should spin slowly or in some cases not at all.  When under load (such as during a parity check), the fan should spin faster.

 

Why choose a PSU with a set fan speed?

 

Again, to save money.  PSUs with variable fan speeds generally cost $10 - $50 more than their static fan speed counterparts.

 

What does Gold/Silver/Bronze/Plus mean?

 

It is a measure of the power supply's energy efficiency at different load levels:

 

% of Rated Load    20%    50%    100%   
80 PLUS 80% 80% 80%
80 PLUS Bronze 82% 85% 82%
80 PLUS Silver 85% 88% 85%
80 PLUS Gold 87% 90% 87%
80 PLUS Platinum 90% 92% 89%
Source

 

As you can see, most PSUs are more efficient in the middle of their load range (around 50%) than they are at either extreme.  Keep this in mind while choosing a PSU for your server.  Your PSU must be able to handle the full power draw of all your hard drives spinning up at once, since this is exactly what will happen during parity checks or the simulation of a failed drive.  However, ideally you also want a PSU that is efficient in the range in which your server will sit idle.  Finding a balance between these two factors is tricky business.

 

 

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Stickied until its no longer useful

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I think it should be noted that some Green drives draw less than 2A on spinup. These values are according to Manufacturer Data Sheets. These are all 2TB drives.

 

WD20EADS - 1.75A

WD20EARS - 1.55A (can be lowered with WD utility)

HD204UI - 2A

5K3000 - 2A

 

I had a question: for the 12v Amp value, is that used by us for drives only, or are we going to have to add some overhead for the motherboard and other devices when sizing a PSU?

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Depends on the power supply but if you get a single rail PSU likes the ones described above then you will have to leave headroom for the motherboard and the like.

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Depends on the power supply but if you get a single rail PSU likes the ones described above then you will have to leave headroom for the motherboard and the like.

 

Yes, I've been only looking at single rail PSU's. So for a potentially 15-drive server and all green drives I'd need 30A for the drives alone (unless I'm using WD Green drives) plus another few amps for overhead. How many amps do the other devices require?

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It varies, and it can be hard to determine exactly.  Here's how I figured out the above number of drives that each PSU can support:

 

Say the PSU has 30A on the single +12V rail.  Estimate green drives at 2A and 7200rpm drives at 3A each.

 

30A/2A = 15 drives, subtract 2 for some overhead, result is support for 13 green drives

30A/3A = 10 drives, subtract 2 for some overhead, result is support for 8 7200rpm drives

 

These are crude calculations, and I'm probably leaving a bit more overhead than is actually necessary (especially since some green drives use less than 2A, as you mentioned), but better safe than sorry, right?

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It varies, and it can be hard to determine exactly.  Here's how I figured out the above number of drives that each PSU can support:

 

Say the PSU has 30A on the single +12V rail.  Estimate green drives at 2A and 7200rpm drives at 3A each.

 

30A/2A = 15 drives, subtract 2 for some overhead, result is support for 13 green drives

30A/3A = 10 drives, subtract 2 for some overhead, result is support for 8 7200rpm drives

 

These are crude calculations, and I'm probably leaving a bit more overhead than is actually necessary (especially since some green drives use less than 2A, as you mentioned), but better safe than sorry, right?

 

That's an interesting way to calc Raj.  Just subtracting 2 drives.  That leaves 4A on the first calc and 6A on the second for overhead.  The 4A feels a little bit tight to me.  I'm shooting for 8A to 10A for overhead on a 15 drive server with green drives so I'd be choosing a 38A to 40A psu for that.  Do you think I'm being too conservative?

 

For a 13 green drive system I'd use a 34A psu.  And drop down to the 30A for 12 green drives.

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I'm inclined to say yes, but again it depends on the specific mobo, CPU, etc. that you are using.  You could do some testing yourself if you have a kill-a-watt or similar.  Boot the server with no HDDs installed (but all fans, etc. that you want to use) and see it pulls from the wall.  Then subtract everything that's on the 5V rail (you'll likely have to consult the PSU's wiring diagram to figure out what to subtract).  Everything that is left should be what is on the 12V rail.  Convert the remaining watts to amps (A = W/V).  That should tell you exactly how much overhead you need.  I would then still add an amp or so buffer above that number, as it seems reasonable to me to assume that a malfunctioning or defective part could pull more juice than it is supposed to, and you would rather that situation not crash the whole server.

 

By the way, the above is all based on my very rough understanding of how electricity, power supplies, etc. work.  I'm no electrical engineer.  If anyone sees any errors in this, please correct me.

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Just heard Corsair is releasing updated versions of their UnRAID-friendly PSU's...they're now 80+ Bronze certified, and I don't know what else has changed. No info on how the "real" manufacturer is yet, either, but we'll find soon enough I guess. Anyway, I though it warrants a post here, since it involves the go-to unRAID psu.

EDIT: forgot the corresponding link: http://techreport.com/discussions.x/20885

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I've started using the TX650 V2 in my 20+ drive builds.  I like it.  In addition to being more efficient (Bronze rated instead of Plus rated), it has a variable speed fan that spins down under low load, much like the more expensive Seasonic PSUs.  Plus it is the same price or sometimes cheaper than the older TX650.  I don't see any other differences between the two PSUs.

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I wouldn't doubt if they're the same PSU's and they just paid to certify them now. This way, they can change the packaging and charge more.

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Well, the variable fan is definitely new.  You might be right about the efficiency rating.

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I wouldn't doubt if they're the same PSU's and they just paid to certify them now. This way, they can change the packaging and charge more.

 

You'd be incorrect.  The old TX series were a mix of Seasonic and CWT based units, while the TX V2s are based on the same Seasonic platform as some of the XFX Core Edition units.

 

Also, if I recall correctly the Antec Neo Eco units are based on Seasonic S12 platform.

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I wouldn't doubt if they're the same PSU's and they just paid to certify them now. This way, they can change the packaging and charge more.

 

You'd be incorrect.  The old TX series were a mix of Seasonic and CWT based units, while the TX V2s are based on the same Seasonic platform as some of the XFX Core Edition units.

 

Also, if I recall correctly the Antec Neo Eco units are based on Seasonic S12 platform.

...which means they're a fine deal, I take it, right? Seasonic is the Mercedes-Benz, as far as I understand - and those new TX's are pretty good value.

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...which means they're a fine deal, I take it, right? Seasonic is the Mercedes-Benz, as far as I understand - and those new TX's are pretty good value.

 

Well, the Antec Neo Eco's are less efficient than more recent PSUs, one of the reasons Seasonic doesn't actually retail those standard S12s anymore (you can get S12 Bronze supplies, though), but they're relatively inexpensive and very reliable.

 

The TX's, new or old, are both very solid supplies, and good values.  If you consider the rebate (I don't usually, but that's just me) the older TX line is probably a better value, but if you don't count on getting that money back, the TX V2s are better units all around, and really nice values, as are the virtually identical XFX Core Edition 650W units.

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I just wanted to toss in here that the Antec High Current Gamer PSUs in the 400W-620W range are based on the very solid Seasonic S12 Bronze platform.  These are a slight efficiency upgrade over the standard S12 (also Antec Neo Eco from 400W-620W).  Internally they are unchanged, and often come at a significant discount vs. their Seasonic branded counterparts.  For example, the Seasonic 520W S12 Bronze is currently $80, whereas the Antec HCG 520W is $60.

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I currently have an array with 16 7K2000 drives.  These are 7,200RPM drives but Hitachi shows the power at 2.0 and not three like has been suggested here for faster drives (should I believe Hitachi?).  I'm getting close to needing more space so I'm looking to replace the Antec case/PSU with a Norco 4224 and have every intent to max it out with 24 drives as soon as unraid supports that many.  I'm waiting for the next great sale on the 5K3000 drives and am trying to figure out the power requirements for the 4224 loaded with all these drives.  I'm leaning towards the CORSAIR CMPSU-750TX (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006).  With a single 60A rail it seems that this should do just fine, no?

 

Also could someone please clue me in on the difference between their normal PSU and the enthusiast line such as this:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139021  It looks like it's justa $5 difference but I'd like to understand what the $5 gets you.

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Other than checking parity it's fairly rare for more than a couple to be spinning but when they are all going one or two will top out at 41-42 and the rest will be in the high 30's.

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^^ That's not too bad. How hot do they get while checking parity on the entire array?

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That is when checking parity on the entire array

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That is when checking parity on the entire array

 

That's not bad then.

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