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[Bug 1130697] Re: Periodic tasks incurs IO performance penalty with LVM imagebackend

To: yahoo-eng-team@xxxxxxxxxxxxxxxxxxx
From: Thierry Carrez <thierry.carrez+lp@xxxxxxxxx>
Date: Thu, 21 Feb 2013 08:56:31 -0000
Reply-to: Bug 1130697 <1130697@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

** Changed in: nova
       Status: Fix Committed => Fix Released

** Changed in: nova
    Milestone: None => grizzly-3

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https://bugs.launchpad.net/bugs/1130697

Title:
  Periodic tasks incurs IO performance penalty with LVM imagebackend

Status in OpenStack Compute (Nova):
  Fix Released

Bug description:
  Using LVM as image backend, periodic tasks (update_available_resource,
  _report_driver_status) can eat up to 10% I/O util rate, which could be
  a serious performance burden in production.

  # iostat -x 1 /dev/sda
  avg-cpu:  %user   %nice %system %iowait  %steal   %idle
             3.01    0.00    2.59    0.50    0.00   93.90

  Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util
  sda               0.00     1.00 2931.00    9.00 23982.00    88.00     8.19     0.11    0.04   0.04  10.70

  
  # dstat -tcd --top-io --top-cpu
  ----system---- ----total-cpu-usage---- -dsk/total- ----most-expensive---- -most-expensive-
    date/time   |usr sys idl wai hiq siq| read  writ|     i/o process      |  cpu process  
  20-02 17:24:32|  3   3  94   0   0   0|   0     0 |SCREEN     2717k 8182B|nova-compute 0.2
  20-02 17:24:33|  5   4  91   1   0   0|  11M   32k|nova-comput  15M 7661B|libvirtd     0.6
  20-02 17:24:34|  9   4  87   0   0   0|4322k 4096B|nova-comput5333k 7772B|libvirtd     8.2
  20-02 17:24:35| 10   3  88   0   0   0|   0     0 |libvirtd     12k  225k|libvirtd     8.3
  20-02 17:24:36| 10   4  86   0   0   0|   0     0 |nova-comput 269k   15k|libvirtd     8.4
  20-02 17:24:37|  8   3  88   0   0   0|3997k 8192B|nova-comput5583k   25k|libvirtd     2.2
  20-02 17:24:38|  3   3  94   0   0   0|3997k 4096B|nova-comput5201k 6398B|nova-compute 0.2

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