I've been researching power and it's still a bit fuzzy to me.  Would someone mind telling me if I can run 15 3TB 7200rpm drives with my current PSU and will my UPS handle it during a power outage?  I'm wanting to begin buying 3TB drives due to the short life span of the green drives that I keep reading about plus the extra storage and speed will be nice.  I also feel like green drives will be phased out eventually anyway. 

 

I'm currently running the following -

- CORSAIR Enthusiast Series TX650 V2 (http://www.newegg.com/Product/Product.aspx?Item=N82E16817139020)

- APC Back-Ups Pro 700 (http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR700G)

 

Would I be able to safely/efficiently run 15x Seagate Barracuda ST3000DM001 3TB 7200 RPM (http://www.newegg.com/Product/Product.aspx?Item=N82E16822148681) with no problem? 

 

If I'm understanding what I've been looking at correctly then I should be able to since my PSU is 53A and each of the previously mentioned HDD should be 3A so we're at 45A from the 15 drives, plus 5A for the mobo we should be ok at 50A correct? I'm not sure how to tell if my UPS can handle it, I would think it's more than enough but I'm really not sure... My UPS is 700VA.

 

 

 

Any input is greatly appreciated. 

In my opinion, you should be looking at a larger UPS.  The unit you have chosen is only rated at 420 watts/700VA.  While the 700VA looks impressive, it is actually the watts that count!  In the case of your intended use, I would be looking at the APC Power-Saving Back-UPS Pro 1000 UPS.  It should provide you with a bit more margin as all of the drives have to be spun up to actually shut the system down.  A too small UPS will result in an instantaneous shutdown of the UPS which  is as bad as not using a UPS at all!

Thanks Frank, so I was looking at the wrong spec.  Will my current PSU handle 15 3TB 7200rpm drives?  I'm assuming so since its 650W and "it is actually the watts that count".  Would someone mind breaking down a quick formula so I can know exactly what I'm looking for in the future? In terms of Watts Seagates site claims an average operating power of 8.0W for the ST3000DM001.  That's all the information I can find on the drive.  According to The Power Supply Thread a non green drive should be "3 amps (36 watts)".  Is that still true?  So we're looking at 540W for 15 3TB 7200rpm drives all spun up at the same time, correct? So the 1000VA should be sufficient since its 600W.  But then you have the Mobo that supposedly draws 5 amps (60 watts) so now we're at exactly 600W. 

 

Given that UPSs will degrade over time shouldn't I be looking to over compensate just a little to ensure it can handle the full load down the road? Should I be looking into something more along the lines of this -APC Power-Saving Back-UPS Pro 1300 780 Watts / 1300 VA (http://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=BR1300G&total_watts=700 )

I didn't see an in between, I would think 650W would be a good point to hit.

 

It isn't the concept of how many times can X fit into Y that's getting me.  I guess it's the lack of information on HDDs when I look at the technical specifications and knowing what's actually relevant (VA, A, W, etc.)

I have also seen the "8W" power spec that Seagate has published and I, too, have seen the "3A" requirement for 'non-green' drives.  I have a distinct suspicion that the 8 watt rating is when the drive is spinning in an idle state.  However, I suspect that the peak wattage most likely occurs when the drive is spinning up during turn-on.  The problem is that when you are shutting down, all of the drives must be spun up simultaneously as a part of the shutdown procedure.  I do suspect that the 3 amp requirement is the absolute worst case scenario and may not be even remotely close to what most hard drives require.  (Unless you are using 10,000rpm drives!) 

 

When you are sizing an UPS, you want to err on the side of safety.  You need for it to be reliable after a couple of three years as its battery ages.  While I have never really timed it, it seems like the time for unRaid to shutdown is approximately two minutes.  To this, you have to add the time that you are willing to wait hoping the power comes back on.  (I have mine set for thirty seconds because I am only a half mile from a LARGE substation.  If it is out for thirty seconds, it will be out for a couple of hours at a minimum!) 

 

My experience of fifteen or so years with UPS's is that the battery will only last two to three years.  When the battery gets to be that old is is a good idea to actually test your UPS periodically.  A 200 watt (or larger) light bulb load is better than simply pulling the plug while your computer is connected to it and turned on!!!!

Hypknox,

 

As you stated, the TX650 V2 has a 53A rail, 15 drives * 3A + 5A = 50A. It should be fine. The 3A is the current required to spin up the drive. The ST3000DM001 has a start up current specification of 2.1A typical. That's a brand new drive. As it ages it will draw more current to start as the bearing wear and lubrication dries up or migrates.

 

Your original UPS is undersized. You'll second choice, the APC Power-Saving Back-UPS Pro 1300 780 Watts / 1300 VA may be marginal for the power supply you have. 650W / 0.80 (efficiency) = 812.5W.

 

As I stated before in another post, never just pull the plug. Use a switched plug. Pulling the plug removes the ground connection and can cause noise glitches and prevent a clean shutdown. I would confuse the USB ports by pulling the plug, by using a switched power strip, the problem went away.

 

PB

Thanks a lot Frank and beck, I understood everything from both of you aside from one piece -

 

the APC Power-Saving Back-UPS Pro 1300 780 Watts / 1300 VA may be marginal for the power supply you have. 650W / 0.80 (efficiency) = 812.5W.

 

Specifically the last part of that, I don't understand where this 812.5W comes from.  I see that the efficiency at full load for the 1300 UPS is 87% per APC's website.  Wouldn't that be 88% of the UPS itself?  Meaning that it would be more like 780W * 0.87 meaning the UPS would handle up to 678.6W at full load?  I was actually thinking the 1300 back-UPS pro would be a bit overkill but didn't see a model in between the 1000 and the 1300.

The 80% is for the TX650 V2. The PS delivers 650W, burns 162.5W internally to function and requires 812.5W as an input.

 

The UPS can deliver 720W, burns 106.4W internally trying to do so and requires 826.4W from the battery.

 

Pout / Pin = efficiency

 

PS:  650W/ 812.5 = 80%

UPS: 720W / 826.4W = 88%, That would be 826.4W from the battery

 

The VA rating is a marketing ploy to appear larger than it is. The TX650 V2 has power factor correction (PFC), therefore the wattage rating is the one to use when selecting a UPS.

 

The APC Power Saving Back-UPS Pro 1500 can deliver 865W

 

Hope this clears things up...

 

PB

 

In response to a PM from Hypknox:

 

Your PSU is fine. As others said, you'll have about 50A of draw with 3A to spare.

 

I agree with the others that your UPS is too small. This should be a better fit:

http://www.apc.com/resource/include/techspec_index.cfm?base_sku=BR1000G

 

I use the above for my entire home entertainment center. Great unit. It is difficult to size a UPS to a server without actually measuring the server's power consumption using a Kill-A-Watt or similar device, but I believe the above UPS should be a safe bet.

Thanks Rajahal, are you basing the statement on the Back-UPS Pro 1000 being sufficient on 15 7200rpm drives or a mix with green drives?  I'm wanting to go full 3TB 7200's, eventually, and am sizing the UPS accordingly.  I hate to keep what should be a closed issue open but I'm getting conflicting information.  beckp seems to think that even the Back-UPS Pro 1300 would be marginal where you say the 1000 would be fine.

 

The price difference between the two is significant, I want to make sure I'm buying the right one.  Also, thank you for the attempt and breaking down the math behind it beckp.  I did appreciate the effort unfortunately I fear I am not following what you're explaining.  I had no idea power was this complex.

 

 

The VA rating is a marketing ploy to appear larger than it is.

In case it helps....

 

Strictly speaking, the VA rating is also a useful figure, but only for those that are in a position to make good use of the data.  A VA rating on a UPS which is much higher than the wattage rating reflects the fact that the UPS is able to drive more highly reactive loads, where the voltage and current are significantly out of phase (where the figure known as the Power Factor is significantly less than 1).  So while it is true that it's the watts rating that should first be checked when looking at a UPS for a home server, a VA rating which is significantly higher can also be seen as a good thing.  The down side is that the vast majority of consumers will not have the appropriate technical background to make use of the information.  That's not to be critical of anyone, it's simply that years ago, UPSs used to be a highly technical purchase only made by big businesses and the power and VA capabilities would have been considered, whereas these days they are widely sold to the public for home PCs and servers.  Maybe a simpler rating system from the manufacturers would help - xxxWatts-A - for best power factor handling, -B for basic, -C for minimal, as an example.

I disagree with the previous statements that the UPS you chose is underpowered. You have to understand that even though you have a 650W PSU and 15 disks, your unRAID server will not use that much power and all disks ALL the time. If it's running and doing it's business, i would be surprised if the whole machine would draw more that 100W... maybe on startup it'll be more, and in idle mode it will be far less.

 

My current PC has a 750W PSU, 8x 2TB disks, and when just running windows and some programs, it uses 120W according to my APC-BR900 UPS (540W/900VA). And when i pull the plug, that BR900 can keep my pc running for 45 minutes...

 

If you take in to account that the primary purpose of the UPS is to SAFELY power down your unRAID machine in a controlled manner, even a few minutes of battery power should be more than enough.

 

If you want to keep the server running for hours at end until the mains is restored, you should get a bigger one. A MUCH bigger one, probably one running on gasoline or dieselpowered but for now i think you'll be fine.

 

Still, one could wonder what happens in the case that the unRAID machine is rebuilding it's par drive or reparing a disk, is there a way to exit quickly and safely from that process when a powerdown occurs and the UPS takes over?

I disagree with the previous statements that the UPS you chose is underpowered. You have to understand that even though you have a 650W PSU and 15 disks, your unRAID server will not use that much power and all disks ALL the time. If it's running and doing it's business, i would be surprised if the whole machine would draw more that 100W... maybe on startup it'll be more, and in idle mode it will be far less.

 

My current PC has a 750W PSU, 8x 2TB disks, and when just running windows and some programs, it uses 120W according to my APC-BR900 UPS (540W/900VA). And when i pull the plug, that BR900 can keep my pc running for 45 minutes...

 

If you take in to account that the primary purpose of the UPS is to SAFELY power down your unRAID machine in a controlled manner, even a few minutes of battery power should be more than enough.

 

If you want to keep the server running for hours at end until the mains is restored, you should get a bigger one. A MUCH bigger one, probably one running on gasoline or dieselpowered but for now i think you'll be fine.

 

Still, one could wonder what happens in the case that the unRAID machine is rebuilding it's par drive or reparing a disk, is there a way to exit quickly and safely from that process when a powerdown occurs and the UPS takes over?

 

I like this line of discussion, but it should not be applied to online UPSs which must handle the power on load. Typical home UPSs are not online but "smart" or switched, not taking the load until the mains drop. That being said, I size my home UPSs for runtime at measured load and do end up buying 750W UPSs for <400W loads because of my desired runtime. The 450W unit's battery is just too small.

 

Get a kill-a-watt, you have fun and learn