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I tested my system on backup and saw considerable degradation in performance when running on backup. Here are the results:

Config:

  1. CPU: 2.0 Ghz, 6 Core, 12 Threads
  2. RAM: 16 GB
  3. UPS: 600W/ 1000VA
  4. PSU: 460W Gold Efficiency
  5. OS: Ubuntu 12.04.3
  6. Software: sysbench

*) Main Power On

andra@Ajax-Alpha:~$ sysbench --test=cpu --cpu-max-prime=100000 --num-threads=12 run
sysbench 0.4.12:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 12

Doing CPU performance benchmark

Threads started!
Done.

Maximum prime number checked in CPU test: 100000


Test execution summary:
    total time:                          32.4046s
    total number of events:              10000
    total time taken by event execution: 388.4964
    per-request statistics:
         min:                                 33.81ms
         avg:                                 38.85ms
         max:                                 50.79ms
         approx.  95 percentile:              38.88ms

Threads fairness:
    events (avg/stddev):           833.3333/1.18
    execution time (avg/stddev):   32.3747/0.01

*) Main Power Off

andra@Ajax-Alpha:~$ sysbench --test=cpu --cpu-max-prime=100000 --num-threads=12 run
sysbench 0.4.12:  multi-threaded system evaluation benchmark

Running the test with following options:
Number of threads: 12

Doing CPU performance benchmark

Threads started!
Done.

Maximum prime number checked in CPU test: 100000


Test execution summary:
    total time:                          40.6918s
    total number of events:              10000
    total time taken by event execution: 487.9980
    per-request statistics:
         min:                                 34.56ms
         avg:                                 48.80ms
         max:                                730.18ms
         approx.  95 percentile:              44.61ms

Threads fairness:
    events (avg/stddev):           833.3333/0.47
    execution time (avg/stddev):   40.6665/0.01

This means the same amount of computation takes 8 extra seconds which is 25% of the time needed when running the server on main power.

I want to know if this is related to less than required backup power available to the server ? or

No matter how much backup power is provided to the server the performance will considerably degrade when running on backup ?

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  • Please describe the server and the power setup in sufficient detail. Jan 5, 2014 at 3:04
  • Yeah, seems like the power supplies may be set up exactly to do that - i.e. you need both but if you're missing one it runs slower.
    – ETL
    Jan 5, 2014 at 3:09
  • @MichaelHampton I have added the details. Thanks for pointing out!
    – i01000001
    Jan 5, 2014 at 3:30
  • @ETL Do you mean the PSU installed on the server ? Is it possible to reconfigure them or they come with this preset power saving configuration ?
    – i01000001
    Jan 5, 2014 at 3:35
  • Ok, my understanding originally was that you had 2 power supplies, not that you went on UPS. I don't see why on UPS your server would slow down, unless it's not getting enough power.
    – ETL
    Jan 5, 2014 at 4:12

1 Answer 1

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On Windows, the OS is capable of detecting when a server is on battery power and throttles the CPU in an effort to conserve power. I wouldn't be surprised if you have something similar configured on your system.

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  • I am running Ubuntu on this server but I do not get the point about OS capable of detecting when server is running on battery power. There is no direct feedback from UPS to the server. Then how would the OS know about it ?
    – i01000001
    Jan 5, 2014 at 3:29
  • You don't have a remote shutdown agent on the server to trigger a shutdown when UPS power gets low? No serial, USB, or network-based device that does this?
    – MDMarra
    Jan 5, 2014 at 4:10
  • Not yet! This question does not arise from a full fledged lab but initial requirement analysis for backup power. I am trying to evaluate the option of giving individual backup to each group of 4 1U servers.
    – i01000001
    Jan 5, 2014 at 4:18

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