[Bug 1006894] Re: Partitions are misaligned when using GPT on disks w/ 4096 byte physical sectors

[Launchpad Bug Tracker]

This bug was fixed in the package partman-base - 153ubuntu5

---------------
partman-base (153ubuntu5) precise-proposed; urgency=low

  * Permit non-cylinder alignment again on GPT (closes: #674894,
    LP: #1006894).
 -- Colin Watson <cjwatson at ubuntu.com>   Mon, 02 Jul 2012 14:54:45 +0100

** Changed in: partman-base (Ubuntu Precise)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1006894

Title:
  Partitions are misaligned when using GPT on disks w/ 4096 byte
  physical sectors

Status in OEM Priority Project:
  Fix Released
Status in OEM Priority Project precise series:
  Fix Committed
Status in OEM Priority Project quantal series:
  Fix Released
Status in “partman-base” package in Ubuntu:
  Fix Released
Status in “partman-base” source package in Precise:
  Fix Released
Status in “partman-base” source package in Quantal:
  Fix Released
Status in “partman-base” package in Debian:
  Fix Released

Bug description:
  [Impact] GPT partitioning always uses cylinder alignment, which is pessimal for performance on most modern disks.
  [Test Case] Do a server install on a blank disk with the 'partman-partitioning/default_label=gpt' boot parameter.  Accept all defaults for partitioning.  Before confirming partitioning, look in /var/log/partman (from tty2); the byte numbers for the start of each partition should be multiples of 1048576.
  [Regression Potential] The plausible things that might go wrong that are worth testing are: (a) it is possible that a bug might cause partitions to be misaligned with things such as large gaps between them or crazy sizes, so check that their sizes look vaguely reasonable; (b) non-GPT partitioning (i.e. in practice the traditional PC MBR partition table format) should not be changed as a result of this work.

  Original report follows:

  I'm doing a fully preseeded install using a partman-auto disk recipe.
  This is an EFI install which obviously uses GPT.  When I launch Disk
  Utility is complains that the EFI fat32 partition and the next ext4
  Linux partition are misaligned by 3072 bytes and 2048 bytes
  respectively.

  When I dump the partitioning out in parted, I can see that the
  partition begins on logical sector 34:

  $ sudo parted /dev/sda unit s print
  Model: ATA ST9500423AS (scsi)
  Disk /dev/sda: 976773168s
  Sector size (logical/physical): 512B/4096B
  Partition Table: gpt

  Number  Start      End         Size        File system     Name     Flags
   1      34s        390659s     390626s     fat32                    boot
   2      390660s    39453160s   39062501s   ext4

  So the partition begins right after the GPT headers, but since this is
  a 4096 byte physical sector drive, this does not begin on a physical
  sector boundary.  It should begin on logical sector 40 (physical
  sector 5) to have proper alignment.

  I'm not sure if this should be filed against partman-auto since this
  is a fully preseeded install or just partman-base.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: ubiquity (not installed)
  ProcVersionSignature: Ubuntu 3.2.0-24.38-generic 3.2.16
  Uname: Linux 3.2.0-24-generic x86_64
  NonfreeKernelModules: nvidia
  ApportVersion: 2.0.1-0ubuntu7
  Architecture: amd64
  Date: Thu May 31 08:45:45 2012
  DistributionChannelDescriptor:
   # This is a distribution channel descriptor
   # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor
   canonical-oem-sutton-precise-amd64-20120523-0
  InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz boot=casper automatic-ubiquity partman/alignment=minimal file=/cdrom/install/preseed.cfg quiet splash -- nouveau.modeset=0
  InstallationMedia: Ubuntu 12.04 "Precise" - Build amd64 LIVE Binary 20120523-03:49
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubiquity
  UpgradeStatus: No upgrade log present (probably fresh install)

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