Ubuntu server unusable due to poor performance

[Kern Sibbald]

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.

[Phillip Susi (psusi)]

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

[Kern Sibbald (kern)]

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
>