misaligned root partition with software raid

[Noa Resare]

A while back I installed Ubuntu 14.04.1 LTS on a home server with two 1T SATA drives. To gain some resilience against hardware failures I set up a software RAID1 using the Ubuntu server install image. Installation was successful but once the system was installed performance was terrible. Inspecting disk activity with iostat revealed 100% utilization and request queue lengths >100. Any read request would stall for a handful of seconds on a mostly idle system.

Investigating this a bit further I can conclude that the inner partition table created by the installer has a root partition that is incorrectly aligned on 63 512byte sectors which causes IO performance to tank. Re-aligning the root partition on the recommended 2048 sectors resolves the performance issues.

Steps to reproduce:

* Hardware with 2 hard drives (I can reproduce this with a VMWare virtual machine with two virtual drives)
* Boot the server install CD
* Create a software RAID1 device
* Choose guided install with the newly created RAID1 device as target

Expected result:
Both inner and outer partition table has partitions set up on a multiple of 4KiB (2048s would be the recommended start offset)

Actual restult:
The first partition on the outer partition table starts on 2048s, but the inner one starts at 63s

Version: The installer available on ubuntu-14.04.1-server-amd64.iso (sha1: 401c5f6666fe2879ac3a9a3247b487723410cf88)

Additional info:
One way illustrating the alignment problem is to run 'parted /dev/md0 align-check opt 1' which outputs "1 not aligned"