[Bug 1005594] Re: Ubuntu server unusable due to poor performance

[Kern Sibbald]

Thanks for trying it. I reported this so long ago, that I had even
forgotten about it. Since I'll be moving up to 14.04 in another month or
two, version 12.04 is less critical.  I suggest that with numbers like
you show below the problem seems to be resolved, so please close the ticket.

Best regards,
Kern

On 04/01/2014 05:38 PM, Phillip Susi wrote:
> I am not able to reproduce this with 12.04.4, are you?  Using a vm with
> a disk of exactly the same size, I get partitions starting at:
>
> 2048
> 999424
> 1499136
>
>
> ** Changed in: partman-partitioning (Ubuntu)
>        Status: New => Incomplete
>

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Title:
  Ubuntu server unusable due to poor performance

Status in “partman-partitioning” package in Ubuntu:
  Incomplete

Bug description:
  Recently I the Ubuntu 12.04 server installed 12.04 on an HP Compaq Elite 8200 with a 1.5TB harddisk Model: ATA WDC WD15EARS-00Z.  I partitioned the disk with guided full disk LVM.  After it was up and running the performance was
  so terrible that the machine was essentially unusable.  After a bit of investigation the problem turned out to be
  the harddisk partition that your partition code did.  It partitioned something like this:

  Disk /dev/sda: 2930277168s
  Sector size (logical/physical): 512B/512B
  Partition Table: gpt

  Number  Start    End          Size         File system  Name  Flags
   1      34s      390659s      390626s      fat32              boot
   2      390660s  890660s      500001s      ext2               boot
   3      890661s  2930277118s  xxxxxxxxxs               lvm   lvm

  where I have left the size of partition 3 out (it is not important).

  It turns out that this partitioning is about as bad as one can do on
  these new disks that have blocks aligned on 8 sector boundaries.

  I repartitioned the harddisk to:

  
  Model: ATA WDC WD15EARS-00Z (scsi)
  Disk /dev/sda: 2930277168s
  Sector size (logical/physical): 512B/512B
  Partition Table: gpt

  Number  Start    End          Size         File system  Name  Flags
   1      34s      390659s      390626s      fat32              boot
   2      390660s  890660s      500001s      ext2               boot
   3      890880s  2930277118s  2929386239s               lvm   lvm

  so that the main disk partition (3) is properly aligned.  I did not
  align the other partitions to save time (I just copied partition off to
  another disk, repartitioned it properly aligned then copied it
  back).  

  The difference in the performance of the system was absolutely
  mind boggling (it felt like it was at least 100 times faster, and
  for many operations it probably was).

  For the command:
  dd oflag=sync bs=4096 if=/dev/zero of=test.xx count=3000

  with the partitioning done by your installer I got:
  12288000 bytes (12 MB) copied, 572.024 s, 21.5 kB/s

  with the aligned partitioning:
  12288000 bytes (12 MB) copied, 156.738 s, 78.4 kB/s

  That is more than 3X the speed.

  If Ubuntu wants to play in the server market, please teach the
  programmers who write the install program to know how to properly
  align the large modern disk.  Hopefully the desktop installer doesn't
  do the same thing ...

  There is no need to answer this as the problem is resolved for
  me, but possibly not for many of your other users.

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