UPS - How big should I get?

[abernardi]

Well guys, I officially have a 9 drive unRAID up and running and serving my HTPC and the rest of the family's storage needs!  Thanks to all who helped me stumble through.

 

I'm planning to move the server into a storage room and I'm guessing it would be foolhardy not to have a UPS on this thing.  My question is, how cheaply can I do this?

 

I have 9 assorted hard drives totaling about 7.75TB of storage.  My PSU is 585W, but I assume that is it's maximum rating.  How do you tell how much power the server is going to pull to spin up all the drives so I can shut it down in case of a power outage?

[bubbaQ]

There are 2 different measurements of a UPS. 

 

1) The first is Watts.  It must deliver enough Watts to run the max Wattage of the equipment.  This is determined by the capacity of the inverter diodes and/or transformer.

 

2) The second is Watt-hours.  This determines how long the UPS will run at a given load.  Watt-Hours is the capacity of the battery.

 

If your system pulls 400 Watts out of the wall, you must have a UPS that is rated at 400Watts or more.

 

If you want to run 400 Watts for half an hour, you need battery capacity of at least 200 Watt-hours (400 Watts * 0.5 hours).

 

These are of course minimums assuming perfect efficiency and 1.0 power factors.  The real world is not so, so add 40% or more to get real-world figures.

 

 

[abernardi]

Are you saying that my 585W PSU will try to pull all 585 Watts?  I thought it would only dole out as much power as needed.

[barrygordon]

Many years ago a bought a little device that plugs into a socket and has a receptcal that you can plug things into.  It has an LCD panel and the panel will readt voltage, voltamps and watts.  So you plug your system into this and watch it as the disks spin up and then watch it in steady state.  You will then have all you need to know.  It is called the kill-a-watt meter.  I have seen it for $39 + Shipping.  Just do a web search. It also sells for $120, so do the search

 

UPS systems have a catch 22, once you have one it will tell you what the power draw is.

 

You are correct.  The rating of the PSU is what it can deliver.  It actually will deliver what it is asked to up to the maximum rating.  It will require somewhat more power than it delivers due to inefficiencies.

[bubbaQ]

Are you saying that my 585W PSU will try to pull all 585 Watts?

 

No, I'm saying that you should not use a 585 Watt UPS to run a system that needs more than 417 Watts (585/1.4).

[abernardi]

Thanks Barry, I'll look into that. 

 

BubbaQ, I guess I didn't make myself clear.  I don't know how much I'm pulling yet, so I don't know what I need.  But I doubt I'm pulling even 300W, though we'll see....

[GK20]

I don't know how much I'm pulling yet, so I don't know what I need.  But I doubt I'm pulling even 300W, though we'll see....

 

you can either

 

(a) use this calculator to get a rough estimation, throw in another 10% on top of final number should be fine

 

http://extreme.outervision.com/psucalculatorlite.jsp

 

or

 

(b) use this meter to get real time reading

 

http://www.p3international.com/products/special/P4400/P4400-CE.html

 

 

[abernardi]

Fantastic GK20, thanks.

[vca]

Well guys, I officially have a 9 drive unRAID up and running and serving my HTPC and the rest of the family's storage needs!  Thanks to all who helped me stumble through.

 

I'm planning to move the server into a storage room and I'm guessing it would be foolhardy not to have a UPS on this thing.  My question is, how cheaply can I do this?

 

I have 9 assorted hard drives totaling about 7.75TB of storage.  My PSU is 585W, but I assume that is it's maximum rating.  How do you tell how much power the server is going to pull to spin up all the drives so I can shut it down in case of a power outage?

 

My system is fairly similar, I've got 8 drives (all Western Digital Greens) totaling 9GB of usable storage, its driven by a 400W Corsair PSU.  My UPS is an APC Back-UPS ES 550 (http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3869826&CatId=233), the status info on it says (with all drives spun up):

 

[pre]

LOADPCT  :  27.0 Percent Load Capacity

BCHARGE  : 100.0 Percent

TIMELEFT :  17.5 Minutes

[/pre]

 

which means the UPS thinks its taking 148W (i.e. 0.27x550W) and can run for up to 17.5 minutes on battery.  You really only need to be able to run for a few minutes to allow the system time to automatically shut down, but longer run time is better as you'll tax the batteries less...  I would think that your system should be within about 20W of this, depending on the type of drives (7200RPM will need more power than greens). These APC UPS boxes are pretty nice and the battery is user replacible.  They are well supported on unRAID by the "unmenu" extension package.  Best of all they are typically in the $60-80 range.

 

Regards,

 

Stephen

[Joe L.]

And, for comparrison.

 

My unRAID servr has 16 drives, none of them "green" and I use an APC Back-UPS ES 750.

 

MODEL    : Back-UPS ES 750

LOADPCT  :  54.0 Percent Load Capacity

BCHARGE  : 100.0 Percent

TIMELEFT :   7.2 Minutes

NOMPOWER : 450 Watts

 

It has a nominal rating of 450 watts and with all the disks spinning I'm drawing a bit over 50% of its capacity.  I'm probably just over its capacity if all the disks were to spin up at the same time.  (the disks draw nearly twice their current draw than they do otherwise when spinning up)

 

It too can often be purchased when on sale for a good price. I seem to remember it being about $50.

 

As you can see, it only gives me 7 minutes of run-time but I have the shutdown set to begin when I have 5 minutes remaining, so in reality, I've got about two minutes on batteries before the server shuts itself  off.

 

Joe L.

[bubbaQ]

UPSes have a nasty habit of overestimating their runtime on battery.

 

1) Do a runtime calibration test every 6 months and put the results on a label on the UPS.

2) Schedule a weekly selftest, and check the results in the log.

3) Put a label on the front of each UPS with the date the battery was last changed. 

4) Replace batteries every 3 years.  If selftests fail, or the runtime calibration shows a significant drop in runtime, replace the batteries.

[chanders]

My system is fairly similar, I've got 8 drives (all Western Digital Greens) totaling 9GB of usable storage, its driven by a 400W Corsair PSU.  My UPS is an APC Back-UPS ES 550 (http://www.tigerdirect.com/applications/SearchTools/item-details.asp?EdpNo=3869826&CatId=233), the status info on it says (with all drives spun up):

 

[pre]

LOADPCT  :  27.0 Percent Load Capacity

BCHARGE  : 100.0 Percent

TIMELEFT :  17.5 Minutes

[/pre]

 

which means the UPS thinks its taking 148W (i.e. 0.27x550W) and can run for up to 17.5 minutes on battery.  You really only need to be able to run for a few minutes to allow the system time to automatically shut down, but longer run time is better as you'll tax the batteries less...  I would think that your system should be within about 20W of this, depending on the type of drives (7200RPM will need more power than greens). These APC UPS boxes are pretty nice and the battery is user replacible.  They are well supported on unRAID by the "unmenu" extension package.  Best of all they are typically in the $60-80 range.

 

Regards,

 

Stephen

 

Hey guys, can one of you explain how to hook this UPS up to my unRAID server? I looked it over but there isnt a USB port at all..

[Joe L.]

What make/model UPS do you have?

[chanders]

Edit: Apparently its a special connector

 

APC Back-UPS ES 550

[gfjardim]

If your UPS didn't came with the cable, you can make one:

 

http://www.apcupsd.com/manual/manual.html#cables

[vca]

Hey guys, can one of you explain how to hook this UPS up to my unRAID server? I looked it over but there isnt a USB port at all..

 

For some reason APC insists on using a non-standard connector on their UPS boxes, so you'll find a socket that looks like a LAN socket, but it really is a USB port (on this model) or a serial port (on older models).  APC supplies a special cable with the UPS that has the appropriate plug at one end and a USB plug on the other.  This cable was included with all the APC UPS units I've bought so far.

 

Regards,

 

Stephen

 

[chanders]

Thanks for the replies guys. Gonna hook this up today!

[seanchronnery]

[pre]

LOADPCT  :  27.0 Percent Load Capacity

BCHARGE  : 100.0 Percent

TIMELEFT :  17.5 Minutes

[/pre]

 

how do you bring up these stats?  I just bought a APC BE550G 550VA.  I think it seems to be working.  Just not sure how to access the stats.  My syslog says;

[pre]

Jan  8 13:55:14 unRAID kernel: generic-usb 0003:051D:0002.0003: hiddev96,hidraw2: USB HID v1.10 Device [APC Back-UPS ES 550 FW:843.K2 .D USB FW:K2 ] on usb-0000:00:1d.0-1/input0 (Drive related)

Jan  8 13:55:18 unRAID apcupsd[1773]: NIS server startup succeeded

Jan  8 13:55:18 unRAID apcupsd[1773]: apcupsd 3.14.3 (20 January 2008) slackware startup succeeded

[/pre]

[BRiT]

apcaccess

 

[seanchronnery]

thanks, BRiT.

 

I see a lot of stats, just not the percent load capacity

 

[BRiT]

It likely scrolled right on past, try scrolling back on your terminal or paging it using less and hitting space to move on to the next page when ready and 'q' to quit.

 

apcaccess | less

[Joe L.]

Your UPS apparently does not provide that information on current load.  Other models from APC do.

 

You'll probably need to use a Kill-A-Watt meter to learn the current draw.

[seanchronnery]

It likely scrolled right on past, try scrolling back on your terminal or paging it using less and hitting space to move on to the next page when ready and 'q' to quit.

 

you're absolutely correct.

thank you.