** Description changed: + [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. + 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)
** Description changed: [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) ** Changed in: partman-base (Ubuntu Precise) Status: Confirmed => In Progress -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1006894 Title: Partitions are misaligned when using GPT on disks w/ 4096 byte physical sectors To manage notifications about this bug go to: https://bugs.launchpad.net/oem-priority/+bug/1006894/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
