[Bug 570805] Re: [regression] dpkg's fsync causes massive regression in Ubuntu Server and Alternate installation times

[Ubuntu QA's Bug Bot]

** Tags added: testcase

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Title:
  [regression] dpkg's fsync causes massive regression in Ubuntu Server
  and Alternate installation times

Status in The Linux Kernel:
  Invalid
Status in Release Notes for Ubuntu:
  Fix Released
Status in “dpkg” package in Ubuntu:
  Fix Released
Status in “dpkg” source package in Lucid:
  Fix Released
Status in “dpkg” package in Unity Linux:
  Invalid

Bug description:
  Binary package hint: dpkg

  dpkg (1.15.5.6ubuntu4) causes a massive regression in the installation
  of the Ubuntu Server.

  Specifically, this from the changelog, addressing Bug #559915:

      - Restore fsync during package unpack (LP: #559915).  This is now done
        by deferring the fsync and rename for normal files in tar extraction
        so that it's done in one pass afterwards, to avoid massive I/O
        degradation due to the serialization from each write + fsync.  When
        creating hard links to normal files on extraction use the .dpkg-new
        filename for source as the file is not yet in place due to the rename
        deferral.

  I just installed the same hardware, from the same USB stick, in an
  identical configuration, one on ext4 and the other on ext3.

  On ext4, this took 19 minutes, 20 seconds.  On ext3, this took 9
  minutes, 8 seconds.

  This is a 100% performance hit on Server installs.  It takes now takes
  over twice as long to install Ubuntu servers.

  While I can understand that the fsyncs() are necessary for power loss
  situations on apt-get upgrade/dpkg operations *after* the system has
  been installed, it should not be necessary at Server install time.  If
  you lose power during a d-i installation, you will clearly need to
  start from scratch anyway.

  The desktop installer does not suffer from this since ubiquity
  installations simply transfer the live image.

  DEVELOPMENT BRANCH: Addressed in a merge from Debian by using one
  large sync before embarking on renames, rather than lots of little
  fsyncs.

  PATCH: http://bazaar.launchpad.net/~ubuntu-
  branches/ubuntu/lucid/dpkg/lucid/revision/95

  TEST CASE: Install Ubuntu Server; measure time taken in "Select and
  install software" step.  Compare 10.04 as released to the 10.04.1
  candidate CD images which should be available for testing in the near
  future.

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