Servers with redundant power supplies

[Ian Blundell]

All of my servers have redundant power supplies that automatically failover.  I have always plugged both power cords into the UPS for that server.  I was talking to TrippLite about a problem I was having with one of their UPS units and they said that I should only plug one power cord into the UPS and the other into a wall outlet. The reasoning was that the 2 power supplies could be overloading the UPS which I don't really buy since I am still only powering the one server aren't I?  The only extra load would be the fan on the second power supply wouldn't it?

I have questions about this configuration:
1.  If the power fails on the UPS but the wall outlet is still good then wouldn't the shutdown software shutdown the server even though there is still good power from the wall outlet?
2.  The UPS normally adds filters and power surge protection,  the power supply direct from the wall outlet would bypass this.
3.  Even if I added a second UPS for the second power supply then would the shutdown software be smart enough to only shutdown the server as the second UPS was running out of power?
4.  Is there a way of knowing and/or controlling which of the power supplies is "primary"?
4.  I am also having problems getting the TrippLite software to run on server 2008 and recognize the UPS.  Do I even need the shutdown software to gracefully shutdown the server?  By the time the UPS is running out of juice then the workstations are all going to be off and there shouldn't be any activity on the server and would it be OK to let it just shutdown when the power runs out?

[Jeff Golas]

I'd leave em both on the UPS.

[Hans Manhave]

Questions I have not really considered.  I have two circuits, two UPS units and one redundent power supply per UPS/circuit.  I didn't install any auto shutdown system.  I have have 30-45 minutes of UPS time and like Ian says, all the work stations will be off by that time.  If I'm present, I will shut down the server if power is out still after 20 or 25 minutes which rarely happens, but does happen.

[Jeff Zylstra]

There's an easy way to find out.  Buy one of those watt miser type appliances that measure how many watts you are drawing, and then alternately plug your server's power supplies into each one to measure power drawn.  They're only about $35, so this kind of expenditure for a server is probably warranted.

[Charlie Charbonneau]

Forgive my ignorance, but isn't the point of redundancy to have the second power supply on an entirely different power source, say a back-up generator or something similar?  having it plugged into the same outlet/ups would really only protect against failure of the physical power supply itself. It seems like it'd be pointless to have a redundant power supply on the same ups.  I could see perhaps a secondary ups for that little extra time in a power outtage, but even that's questionable.

[Jeff Zylstra]

Forgive my ignorance, but isn't the point of redundancy to have the second power supply on an entirely different power source, say a back-up generator or something similar?  having it plugged into the same outlet/ups would really only protect against failure of the physical power supply itself. It seems like it'd be pointless to have a redundant power supply on the same ups.  I could see perhaps a secondary ups for that little extra time in a power outtage, but even that's questionable.

You're displaying wisdom, not ignorance.  I can say that since I'm of the same opinion.     Although servers should be on a dedicated circuit, I bet you that half of the folks here don't have it set up that way <sound of scurrying IT folks checking electrical connections>.   Electricians will tell you that this save a lot of hassles.  That said, if that circuit breaker trips, I would think that a failover should happen and the another live circuit and power supply should take over.

[Billy Welsh]

Forgive my ignorance, but isn't the point of redundancy to have the second power supply on an entirely different power source, say a back-up generator or something similar?  having it plugged into the same outlet/ups would really only protect against failure of the physical power supply itself. It seems like it'd be pointless to have a redundant power supply on the same ups.  I could see perhaps a secondary ups for that little extra time in a power outtage, but even that's questionable.

You're displaying wisdom, not ignorance.  I can say that since I'm of the same opinion.     Although servers should be on a dedicated circuit, I bet you that half of the folks here don't have it set up that way <sound of scurrying IT folks checking electrical connections>.   Electricians will tell you that this save a lot of hassles.  That said, if that circuit breaker trips, I would think that a failover should happen and the another live circuit and power supply should take over.

Also depends on the limitations of your space.  If your server closet was originally something else, and it got "converted" to the data closet, you may not have the "luxury" of 2 dedicated circuits.  At least you are getting protection from the main power supply in the server going out - I agree it is a minimum level of protection but it's still better than relying on a single power supply.  I have changed my share of those, some of them in servers, so I am very glad to know there are 2 in my current box.

[Jeff Zylstra]

Power supplies are one of the components most likely to die on a server.  Unfortunately, they're not "universal" anymore.  Especially in the Dell machines that I've worked on.  More and more are proprietary.  That's a shame because I still have a 600 Watt spare in my computer room that I'll probably never use.

[Hans Manhave]

One reason to put either both PS units on the same UPS or each PS on its own UPS could be to have the power filtered from surges and other nasty evil doers.  Without a UPS one exposes the heart of the operation to a higher likelihood of harmful electrical mishaps.  Sure, we have a breaker box protection device.  I have multiple circuits going into my closet.  And I'm fortunate enough with this 100+ degree weather to have three a/c units each capable of cooling my office/closet to acceptable temperatures.  But no power feed should be left unprotected from surges etc.

[Bloody Jack Kidd]

primarily, redundant power supplies are to protect you from PSU failures - not to power alternate power feeds from different inputs. However, they can be used that way to extend your N+1 practices. I would not plug one into a UPS and another into a wall socket though, that seems odd.

[Ben Thoele]

I had two APC SUA1500s that were setup as dual path power to two dedicated ground circuits and feeding our two Dell R610s.  We put a AP9618 management card in one of the two APCs since it a virtual environment.  Since the Sealed Lead Acid Batteries were end of life and they don't last long in a UPS, which is a little easy bake oven I externalized then.  I drilled a hole in the side of the case the ran the cable connector out to some large deep cycle solar grade batteries.  The only issue we had was the voltage range of a Flooded Lead Acid is a little slower than a Sealed Lead Acid Batt so the UPS doesn't even touch the capacity of the new batteries and the UPS cuts out sooner than we hoped.

[Mark]

Your UPS should be specked to support your specific server, including number of power supplies, and also along with anything else plugged into it.  UPS's are almost ALWAYS specked incorrectly.  We tend to keep them longer than other hardware, and they are expensive.  Hell, even Dell will sell you and underpowered UPS when you buy it as a package deal with new servers!

All that said, plug BOTH of them into the SAME UPS.  Sure, you could try to balance them between UPS's but I'd suggest shying away from that.  If you get an additional UPS, balance the load by device/power usage -- not by power supplies.  Besides the fact that you'd likely end up out of balance, you're not really doing yourself any favors by splitting them, in my opinion.  Been there, done that.

Also, I haven't installed any additional software to monitor UPSs.  I wanted to at some point and drive myself crazy trying to find something to fit what I pictured.  The end result for me was just the Windows built-in battery meter and some scripts.  The nice thing about using scripts is that you can use IF statements, you can remotely shutdown everything from a single source, you can send emails and text messages (or if you're using Asterisk, even trigger an automated phone call!).  I'd suspect you'd have to pay money to get all those features in the same product.

Just a reminder: these are my opinions.  Some directly from experience, some just based on experience + additional consideration.

[Jeff Zylstra]

I don't run any UPS software on any of my computers.  I bring in my laptop about once a year and plug it into each one of the UPS units to check remaining battery life, etc....  If it gets less than 10 minutes, I replace the battery.  UPS units are hard on batteries because they're constantly overcharging them.  Most batteries are designed to be discharged and then recharged.  If you don't do that, you can easily create a "memory" in the battery to the point where it won't hold as much of a charge anymore. 

[Mark]

I think that's old tech, Jeff.  what kind of UPS are you using?  My UPS tells me the load, the charge, and when to change the batteries.  See pic.

EDIT:  Also, my UPSs are under spec'd based on everything I said in previous post.  In addition to that, they are only meant to keep the systems alive long enough to shut down gracefully.  If we want an hour of battery life, we'd be looking at nearly $10,000 for a single UPS.   The cheapest one I spec'd on APC.com was around $7,700 I think.  We have a decent generator, so if the power is out long enough, I just fire that baby up, run some custom extension cords, and we're back in business.  Of course, I plug each UPS into the generator to ensure clean power.

[Mark]

Here is the direct link for the APC calculator: http://www.apc.com/tools/ups_selector/index.cfm

Choose the one in the middle for "Configure by devices"

[Jeff Zylstra]

I think that's old tech, Jeff.  what kind of UPS are you using?  My UPS tells me the load, the charge, and when to change the batteries.  See pic.

EDIT:  Also, my UPSs are under spec'd based on everything I said in previous post.  In addition to that, they are only meant to keep the systems alive long enough to shut down gracefully.  If we want an hour of battery life, we'd be looking at nearly $10,000 for a single UPS.   The cheapest one I spec'd on APC.com was around $7,700 I think.  We have a decent generator, so if the power is out long enough, I just fire that baby up, run some custom extension cords, and we're back in business.  Of course, I plug each UPS into the generator to ensure clean power.

Oops.  I was referring to the UPS units that I have on all of the workstations, not the server unit.  The smaller ones don't have any LED lights, so I have to plug into those periodically.  My big rackmount APC 1500 does have those lights, but invariably we have a power outage and someone's computer goes down or reboots.  Then they're mad at me because they've lost work or were inconvenienced when no one else was.  Once a year probably isn't enough, but it's what I can manage.

[Mark]

ahh, makes perfect sense!  I wish we had those.  I am jealous!

[Jeff Zylstra]

ahh, makes perfect sense!  I wish we had those.  I am jealous!

All it takes is for a computer to reboot when someone is doing the most important proposal of their life, and you'll have them soon enough.  I think the UPS units were like $50 apiece, or maybe less than that.  But we also have we have a generator that demands that we have something to filter the power from the generator.  Without that filter, the computers won't even run on generator power alone.

[Mark]

Yep, I know how that goes.  Our power has gotten better in the past few years, but we use to lose it a lot.  Our generator is not wired into the building.  It is big enough to power the phones and data equipment and one or two workstations which is all we would need.  If we ever have a prolonged power outage, we'll send people home with a CD or thumb drive that gives them all remote access.  I can even fire up some SIP extensions if necessary.

I can't see them buying 32 UPSs though.  Maybe a few critical ones, but then batteries are another expense.  This comes up every two years or so around here and we just haven't done it yet.

[Jeff Zylstra]

Yep, I know how that goes.  Our power has gotten better in the past few years, but we use to lose it a lot.  Our generator is not wired into the building.  It is big enough to power the phones and data equipment and one or two workstations which is all we would need.  If we ever have a prolonged power outage, we'll send people home with a CD or thumb drive that gives them all remote access.  I can even fire up some SIP extensions if necessary.

I can't see them buying 32 UPSs though.  Maybe a few critical ones, but then batteries are another expense.  This comes up every two years or so around here and we just haven't done it yet.

I understand.  We've had 2 multi-day power outages because of ice storms and 1 from a tornado, so getting a generator wasn't a choice.  We HAVE to up and operational, even if no one else is.  The funny part is that the power lines are down across our street half of the time, so the police close our road half of the time.  But we can park on a side street and walk, so we do what we have to.

[Jim Jensen]

Since we have some people here with experience with generators, help a guy out a little - I've been tossing around the idea with a friend about buying one that we can have together as a disaster plan for each of our agencies. The chances of both of us being out of power is not terribly great. Ice storm would be the most likely reason and they usually spread their outages enough to be in our favor - we're about 3 miles apart on completely different main service lines. In a worst-case scenario, we'll forward one offices phone lines to the other and temporarily co-locate.

So - how big of a generator do we need? We would want to run a server, plus 2-3 workstations if we can, plus a phone main box that doesn't draw much energy. I've never known much about how much wattage I'd need or doing the wattage conversion for computers, etc.

[Ian Blundell]

Watts = Volts x Amps so a regular 110v 20amp circuit would be 2,200 watts.  If you think that you could plug your servers, workstations, etc. into a single circuit without it tripping the breaker then that should give you an idea of the size of generator you would need.

[Mark]

And remember to ALWAYS plug the UPS into the generator.  Do NOT plug your equipment directly into the generator.

[Jeff Golas]

Watts = Volts x Amps so a regular 110v 20amp circuit would be 2,200 watts.  If you think that you could plug your servers, workstations, etc. into a single circuit without it tripping the breaker then that should give you an idea of the size of generator you would need.

Should always up the need a little bit as most generators are rated for "peak" current - meaning 2200 watts would be running the thing at full tilt and having it probably run hot. If you used a 3000w generator it wouldn't be taxed 100% of the time.

[Jim Jensen]

Watts = Volts x Amps so a regular 110v 20amp circuit would be 2,200 watts.  If you think that you could plug your servers, workstations, etc. into a single circuit without it tripping the breaker then that should give you an idea of the size of generator you would need.

I've no idea. Short of plugging them all into as an experiment, I'm nowhere closer. Paging Dr. Hans -- I believe you've run some meters to measure such a number.

[Hans Manhave]

Watts = Volts x Amps so a regular 110v 20amp circuit would be 2,200 watts.  If you think that you could plug your servers, workstations, etc. into a single circuit without it tripping the breaker then that should give you an idea of the size of generator you would need.

I've no idea. Short of plugging them all into as an experiment, I'm nowhere closer. Paging Dr. Hans -- I believe you've run some meters to measure such a number.

Assuming that I'm being referenced, I'll add what I know.  Didn't see the message till now.  Must submit forum enhancement (tapatalk or Simple Machines) to e-mail me when certain words (like my name) are being used. 

I have a device to measure wattage use that plugs in between the wall socket and the device.  Kill-A-Watt or something like that it is called.  Inexpensive and fun to play with.  You could measure between the UPS and the wall, then add them up plus some extra. 

We have run this office on a several generators for several days during the ice storm of December 2000 (I think it was then).  We laid a whole wire tree down the length of the office, with Romex, junction boxes etc.  We used the UPS units to plug into that.  There were not many problems.  We used those generators that welders carry on their pickups or trailers.  If you do use those, make sure you make it next to impossible to remove them without certain equipment because they are often stolen in this part of the country.

Running full size office printer/coper/scanner/fax machines may not be possible.  They draw an enormous amount of power on startup.  But in those emergencies, one may just bring one or more inkjet units from home.

Remember to provide power for the internet router, network switches and other such easily overlooked closet material.  Also remember the phone system!

[Jim Jensen]

Not that Facebook is a medium to copy, but it would be interesting if we had the ability to 'tag' someone in a post and have it notify them.

So do you have a rough idea what size generator was able to run a certain number of computers?

[Gene Foraker]

I have the Kill-a-watt device Hans mentioned.   It is fun to work with.

The best small generators are the Honda EU2000i.    2000 honest watts and they are small, light weight, easily stored and transported and whisper quiet.   They are VERY popular with RVers and boaters.   You can get the companion unit which hooks two together in parallel to double your power.   They cost under $1000 each.   They claim the power output is stable enough for computers.

[Gene Foraker]

Oh, to answer how much power you need, look at the printer.   Laser printers take up gobs of power.   You might be able to get away with 2000 watts to power a server, one workstation and a printer, but I think two of the Honda units I mention below would be better and you could throw in another workstation or two.

[Ian Blundell]

How long an extension cable can you use with these generators?  They have to be outside when they are running and we are up on the 2nd floor with the computer room in the center of the building away from any windows.
We would also need to power internet/phone equipment in the basement.  Wonder if we could just run those on a UPS since they probably don't take much power.

[Gene Foraker]

Ian, we were talking more about a disaster situation where you might move a minimal amount of equipment to a secure location, either in your building or maybe even off site at a temporary location.   There is voltage loss for long runs of cable and tables where you can look up the voltage loss for a given wire size and length of run.   The voltage loss would increase the amp draw and lower the effective amps available to the device.   Given top quality 12 gauge or better cables, I would not run much beyond 150 to 200 feet.  I have access to the voltage loss tables for 12 volt, but not 120 volt.    Second story would not be a problem at all if you can get a nearby window open.

For supplying power to existing multi-server locations and through out a multi-story building you likely need a commercial generator running on either diesel or natural gas.

Phone systems can run for hours on a simple UPS, but if we are talking a disaster where power lines are down for long, then I'd guess phone and internet lines to be down also.   You can set up the phones to be forwarded to cell phones by your phone provider.   Internet would have to be wireless.

Addition - I just found several voltage drop calculators:

http://www.csgnetwork.com/voltagedropcalc.html

http://genuinedealz.com/voltage-drop.html

[Ian Blundell]

We had a power outage recently.  A storm on Saturday at 8pm took down a pole and the power to our complex along with lots of others in the state.  On Sunday when the power company hadn't even been out to identify the problem never mind give us an estimate on when we would get power back we declared a disaster with Agility and they arranged to send us a generator.  A hugh generator arrived Monday lunchtime but because Hertz screwed up it wasn't up and running (with a couple of big extension cables and spider boxes till late in the afternoon.  We did get all of the servers and about a dozen workstations up and running.  That is when we discovered that equipment in the basement needed power for our T1 phone & data lines, along with the cable & FiOS internet connections to work.  We did have calls forwarded to our 4 backup POTS lines but were unable to do little more than explain the situation and take messages.  The power came back up on Monday evening so we only got a couple of hours use out of the generator.
I finally managed to get an electrician to give me a quote on installing a power transfer switch so that the generator could just hook up to a switch on the outside of the building but I don't think that management is going to spring $13K for that option.  The alternative is to have an electrician come out (if we can get one if there is a wider area-wide problem) to hardwire the generator into the main power supply in the basement after Agility deliver the generator (Agility will help us find an electrician if we can't get a local one but that will only add to the delays).
We are looking at various options to get us through the first couple of days if we are out of power but the building is still OK.  Having one or more smaller generators on hand to get the minimal amount of equipment up & running is one of the options we are looking at.

[Jeff Zylstra]

$13 K for a power transfer hookup?  Wow!  We spent less than that for our generator and power transfer switch!  It's just a 25KW single phase Generac generator that runs on natural gas, but it works fine for us.  Our power in the building is divided into 4 different breaker boxes - 2 for each side of the building.  Rather than feeding individual circuits, the power transfer switch feeds 2 of the 4 breaker boxes.  The other side of the office isn't a mission critical operation, so they're on their own for power.   You may want to find out if dealing with it on a circuit by circuit basis is what is causing that quote to be so expensive.

[Gene Foraker]

$13 K for a power transfer hookup?  Wow!  We spent less than that for our generator and power transfer switch!  It's just a 25KW single phase Generac generator that runs on natural gas, but it works fine for us.  Our power in the building is divided into 4 different breaker boxes - 2 for each side of the building.  Rather than feeding individual circuits, the power transfer switch feeds 2 of the 4 breaker boxes.  The other side of the office isn't a mission critical operation, so they're on their own for power.   You may want to find out if dealing with it on a circuit by circuit basis is what is causing that quote to be so expensive.

At the very least get some alternate quotes from other sources.   Every area has at least several companies who sell and install permanent generators.   Call them and ask who the electrical firm is which installs the transfer.   Make sure they understand that it is not an automatic standby installation such as needed by a hospital.

[Jeff Zylstra]

$13 K for a power transfer hookup?  Wow!  We spent less than that for our generator and power transfer switch!  It's just a 25KW single phase Generac generator that runs on natural gas, but it works fine for us.  Our power in the building is divided into 4 different breaker boxes - 2 for each side of the building.  Rather than feeding individual circuits, the power transfer switch feeds 2 of the 4 breaker boxes.  The other side of the office isn't a mission critical operation, so they're on their own for power.   You may want to find out if dealing with it on a circuit by circuit basis is what is causing that quote to be so expensive.

At the very least get some alternate quotes from other sources.   Every area has at least several companies who sell and install permanent generators.   Call them and ask who the electrical firm is which installs the transfer.   Make sure they understand that it is not an automatic standby installation such as needed by a hospital.

Ours actually is an automatic standby as the generator senses the lack of power and automatically starts itself and automatically transfers power from the utility company inputs to the generator.  I think the electrical hookup came to around $1,200 and the generator was about $10-11K.