[Bug 742164] Re: detects bad alignment but doesn't correct it

[Phillip Susi]

You requested that the partition start at 0 MB.  Parted tries to find
the closest valid location within half of a MB, which is at 16 KiB.
That is not aligned to a multiple of 1 MiB.  You might use a start of 0%
instead, which will give a large enough search radius to to snap to the
optimal alignment.


** Changed in: parted (Ubuntu)
       Status: Confirmed => Invalid

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Title:
  detects bad alignment but doesn't correct it

Status in “parted” package in Ubuntu:
  Invalid

Bug description:
  Binary package hint: parted

  As a follow-on from bug 742123 (and on the same hardware, and also on
  Maverick):

  'parted -a optimal' seems to be able to detect when partitions are
  misaligned, but it doesn't correct the allocation of new partitions to
  make them aligned, nor tell me how they should be aligned.  This is
  very unhelpful.

  
  mbp at joy% sudo parted -a optimal /dev/sdb
  GNU Parted 2.3
  Using /dev/sdb
  Welcome to GNU Parted! Type 'help' to view a list of commands.
  (parted) print                                                            
  Model: ATA ST9750420AS (scsi)
  Disk /dev/sdb: 750GB
  Sector size (logical/physical): 512B/4096B
  Partition Table: gpt

  Number  Start  End    Size   File system  Name                  Flags
   2      250GB  750GB  500GB  ntfs         Basic data partition

  (parted) mkpart primary ext4 0 250GB
  Warning: The resulting partition is not properly aligned for best performance.
  Ignore/Cancel? c                                                          

  Changing the units to cylinders and then making a new partition on
  whole cylinder boundaries means this message does not appear.  But
  from what I understand, the optimal alignment for modern disks is not
  cylinder boundaries, and the cylinders for this disk are not evenly
  sized.

  
  (parted) unit cyl                                                         
  (parted) print                                                            
  Model: ATA ST9750420AS (scsi)
  Disk /dev/sdb: 91201cyl
  Sector size (logical/physical): 512B/4096B
  BIOS cylinder,head,sector geometry: 91201,255,63.  Each cylinder is 8225kB.
  Partition Table: gpt

  Number  Start     End       Size      File system  Name                  Flags
   2      30394cyl  91201cyl  60807cyl  ntfs         Basic data partition

  (parted) mkpart                                                           
  Partition name?  []? base                                                 
  File system type?  [ext2]? ext4                                           
  Start? 1                                                                  
  End? 30393                                                                
  (parted) print                                                            
  Model: ATA ST9750420AS (scsi)
  Disk /dev/sdb: 91201cyl
  Sector size (logical/physical): 512B/4096B
  BIOS cylinder,head,sector geometry: 91201,255,63.  Each cylinder is 8225kB.
  Partition Table: gpt

  Number  Start     End       Size      File system  Name                  Flags
   1      0cyl      30393cyl  30392cyl               base
   2      30394cyl  91201cyl  60807cyl  ntfs         Basic data partition

  (parted) align-check                                                      
  alignment type(min/opt)  [optimal]/minimal?                               
  Partition number? 1                                                       
  1 aligned

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