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Best option for UPS on a budget for a Dell poweredge 1950

Posted on 2011-10-19
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Last Modified: 2012-05-12
We  have a Dell PowerEdge 1950 that was donated through a grant to us (non-profit) a few years back.  We need a UPS to power it but are on a very limited budget.  We are not worried about long runtime so much as just making sure it can shut down gracefully.  It's a fileserver and DC, no exchange or SQL.  The issue is it has dual power supplies, each one being about 670W according to Google.  

Question is, does the server pull full power from each PSU during normal operation?  We realilze ideally each PSU would have it's own UPS, but that may not be plausible unless absolutely necessary.

We are trying to find a good price on a name brand UPS that will meet its requirements, but really trying to stay at or under $ 200.

Thanks
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Question by:Jsmply
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by:Amit Khilnaney
Amit Khilnaney earned 336 total points
ID: 36996535
Dual power supplies is there for high availability, you need to connect two power supplies to two different UPS to take full benefit.

No, the server do not pull the full power during normal operation but it still depends on the number of users trying to access it i.e. fileserver purpose...


U need to monitor the power usage under different load conditions before determining the ups needed if you are not buying the ups according to full load marked on PSU..

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by:Amit Khilnaney
ID: 36996547
U can get a fair idea about power usage of system from this tool. There are many tools but i use this one at my desktop. and power usage goes to 230 W while playing games otherwise it remains at around 70-80W with Corei5 and Cooler Master GX 650W PSU x 1 under normal condition while running windows 7.

http://www.cpuid.com/softwares/hwmonitor.html
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by:Dr. Klahn
Dr. Klahn earned 336 total points
ID: 36997231
Since switching power supplies are reactive loads, a UPS supplying a single 670W supply should be rated at least 1 KVA.  (see the Wikipedia article on power factor.)  A UPS should always be configured in terms of peak power demand, not average use, to prevent nasty surprises when it is actually required to perform.

I would configure at least a 1500VA UPS on each power supply to handle the server alone.  If a single UPS is contemplated to serve both supplies, 2500VA would be appropriate.  Depending on how long the system is expected to run during a failure, and whether any peripherals such as a network firewall or a display are also connected to the UPS, a higher rating may be appropriate.

APC UPSes are the industry standard.  They are well supported, the software is readily available for both single-machine and multiple-machine installations, they are readily available used, and they use readily available batteries when the time comes for replacement.  If you purchase APC you will not regret it later.
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by:Sebastian Talmon
Sebastian Talmon earned 332 total points
ID: 36997862

hey - the question was not "what is best practise for an ideal solution" but a low-budget solution.


- you do NOT need to use an UPS for both power supplies...  There are two power-supplies for redundancy, so that if one power-supply fails, the server continues running. That also means, that if power on one power-supply is lost, the one that is powered with an UPS could take the full load, the server is still fully functional (just the fan of the now full-loaded power supply would spin up and generate more noise ;-). => A single UPS for one of the power supplies would be sufficient.

- peak power demand does NOT depend on the maximum power of the power-supply...  It depends on what the server really needs (mainboard + processor + count of HDDs). If you only have two harddisks in the server, the server does not need the full 670W

So I would recommend a single UPS with  1000 VA  (APC SmartUPS 1000VA), connected to one of the power supplies.
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Author Comment

by:Jsmply
ID: 36997998
Thanks.  Tacotec, just to clarify, using your solution, in the event for whatever reason the power supply that was plugged into the UPS failed and the power flickered or went out, we would end up with an ungraceful restart or shutdown of the server, correct?  

Granted it's not likely to happen as hopefully the failed power supply would be noticed, but still.
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Author Comment

by:Jsmply
ID: 36997999
Oh and yes, only 2 HDDs, simple Raid1.
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Expert Comment

by:charlestasse
ID: 36999672
The 1950 will pull 670W MAX. with with one PS running or with 2 splitting the load (redundancy)
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by:Sebastian Talmon
ID: 37000363

yes - if the power-supply that is connected to the UPS failes DURING an power-outage, then the server is down.

if the power-supply failes without an power-outage, the second power-supply would take over the full load


You could also connect BOTH power-supplies to the same UPS (as charlestasse said, the 670W is the maximum of BOTH - so one power-supply could handle the full load)  -> in this configuration one power-supply could fail also during power-outage, BUT if the UPS is damaged, the server is down...

personally I think that the risk of an UPS failure is higher than an power-supply outage just in the moment of an power-outage...  (but both scenarios should allmost never hapen)
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by:charlestasse
charlestasse earned 332 total points
ID: 37001655
The primary purpose of a BASIC (NON Enterprise) UPS is to allow you time to shutdown connected devices when power is lost. Not for Power Protection and Not for Keeping your devices up and running while waiting for power to be restored.
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by:Callandor
Callandor earned 332 total points
ID: 37002859
You might find some APC UPS units on ebay that are being sold off from companies that have gone under.  I have picked up a few this way.  The shipping cost will be high, though.
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Author Comment

by:Jsmply
ID: 37003807
Thx. If the conclusion is we want a 1000va and that will handle one of the power supplies, we should be able to find that.
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by:charlestasse
ID: 37006761
Check out Dell's 1000w Rack and Tower systems
dellups.com
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aleghart earned 332 total points
ID: 37020103
This is a decent deal (with free shipping):  APC BackUPS Pro 1500VA

For larger capacities, we've found good budget deals at CDW's outlet (hit-or-miss, depending on current inventory).  One 1500VA rack-mount unit had a "wrong" plug end for the user, so we picked it up for 1/2 price and replaced the plug end.  Warehouses are in Chicago and Las Vegas.

Another supplier we've used is RefurbUPS.com.  Good price on older UPS network cards.  Shipping from NY, so check the costs first.

I don't think TechSoup has vendors who provide UPS equipment, but I may be wrong.
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Author Comment

by:Jsmply
ID: 37020267
Thanks!  That Amazon deal should work great.  

Quick question - with this APC 1500VA do we still only want to run one power supply into the UPS?  If so, should we simply connect the other PSU to the surge protected only outlets on the UPS?

Thanks
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Expert Comment

by:aleghart
ID: 37020370
Plug in both PSU...no harm in that.  If you're nervous about UPS hardware failure, then plug the other PSU into the wall on a SEPARATE circuit.  In the future, you can get another UPS for the second PSU if you feel the need.

The redundant PSU is to avoid hardware failure of a single PSU.

A second power circuit will avoid accidental tripping or switching, which takes out both PSUs at the same time.

A second UPS on a separate circuit gives the most redundancy...if the power goes out completely, and you have a single UPS failure, the second UPS will take over.  And yes...it has happened.

If it were me, I'd plug in one PSU to the UPS and the other PSU to an outlet on a separate circuit.  But that's only because I know where all my circuits are going...little chance of someone messing up the wiring or getting to the breaker panel.  If in doubt, put both PSUs into the UPS.
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by:aleghart
ID: 37020374
Yikes....don't forget to connect the cable and install the automatic shutdown software!
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Author Comment

by:Jsmply
ID: 37020600
Thanks.  Probably wouldn't be easy to get to a second circuit where the server cage is situated here.  Would be nice though.

If we connect both PSU's into the UPS, should one go through surge only or do you believe the UPS can handle the load on both?

Thx
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Expert Comment

by:aleghart
ID: 37020834
Load is almost the same, whether you have one PSU plugged in or both.  It's the total load of all components + "overhead" of 1st PSU + "overhead" of 2nd PSU.  The overhead is the nominal wattage required to keep the PSU active, power the fan on idle speed, and power the LED status lights.  That should be insignificant..

The greatest load is at power up, which is when all drives are spinning, and all fans run at full speed for about 10 seconds.  That load (by specification) can't be higher than ~600W, since that is the limit of the PSU.

Hope that helps.  Short answer: no problem.
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Author Comment

by:Jsmply
ID: 37020968
Thanks.  So even though both power supplies are rated for 675W, they will never both pull 675W so its okay to connect them both to the 1500VA/875W UPS?  

If both PSU's are getting good power (either through the AC Utility power or off the battery) will the server pull all the power for the components from one PSU or divide the load?  IE: if it takes 400W for the server to run normally with it's normal components, will it pull the 400W from one or 200W from each PSU?

On a sidenote: will connect the data cable as you stated, but do you know off-hand if the APC PowerChute software will work with this APC (Back-UPS Pro) and Win Server 2003?  Last time we checked with APC they said the Back UPS (non-pro) software was designed for non-server OS'ses but we could use native Windows power management.
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Expert Comment

by:aleghart
ID: 37021067
Both PSUs will not run at full load at the same time.  They are redundant supplies (N+1).  Whether it's switched full load onto one PSU or shared between the two PSUs is up to the hardware configuration.

With 3 PSUs, N+1 redundancy means that the total load can be handled by 2 PSUs.  And so on.

The unit I linked to is a "Pro" model.  There is also a connection for an extra battery pack to increase your runtime. BR24BPG is the matching color.


IIRC, Windows power management should work fine.  The specs list PowerChute "personal edition" is included for free.  I think they are charging for servers now.
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Author Comment

by:Jsmply
ID: 37021081
Thanks.  so at no point can both PSU pull 675W each?  Where would you find out the max each would pull?
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Author Closing Comment

by:Jsmply
ID: 37021091
Thx all, Aleghart if you don't mind still clarifying the last question that would be great.  Didn't want to leave the original question open though.
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Expert Comment

by:aleghart
ID: 37021174
If the power supply says "redundant (N+1)", then the system is designed to operate while one PSU is fully removed.  So, take the max rating of the remaining PSUs, add a small percentage for the overhead of the "spare" PSU, and you have your theoretical max load.  So, for  675W, your system should never pull over 700W.

I think without drives, those servers pull between 350-300W.  That leaves you 300+ watts for hard drives.  At ~10W or so per drive, you shouldn't be anywhere near the max of the PSU.
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Author Comment

by:Jsmply
ID: 37021188
Ah, gotcha.  That makes sense.  So anotherwords, both drives can be connected to the battery side of the UPS because really even at full load the PSU's can't pull more than the max that one PSU would be able to pull (system at full capacity) + the minor overheard for the other PSU.
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Expert Comment

by:aleghart
ID: 37021400
Correct.
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Author Comment

by:Jsmply
ID: 37021533
Thank you!
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