Cannot reduce number of components in RAID array

[Pete Stephenson]

Binary package hint: gnome-disk-utility

1. Version of Ubuntu:
Description: Ubuntu 10.04 LTS
Release: 10.04

2. Version of package:
  Installed: 2.30.1-1
  Candidate: 2.30.1-1
  Version table:
 *** 2.30.1-1 0
        500 http://us.archive.ubuntu.com/ubuntu/ lucid/main Packages
        100 /var/lib/dpkg/status

3. What do I expect to happen:
a. Create new RAID-1 array with 2 components using the gnome-disk-utility GUI. Have the array build and report the array status as "Running".
b. Add a new component to the array using the Edit Components GUI and the "Expand Array" option. Have the array report "degraded" and sync the new component. After rebuilding the array, gnome-disk-utility reports the total number of components in the array as "3" and the status of the array as "Running".
c. Remove a component from the array using the Edit Components GUI. The selected component is removed from the array. gnome-disk-utility reports total number of components in the array as "2" and reports the array status as "Running".

4. What happened instead:
a. Created new RAID-1 array with 2 components using the gnome-disk-utility GUI. Had the array build and report as "Running".
b. Added a new component to the array using the Edit Components GUI and the "Expand Array" option. Had the array report "degraded" and sync the new component. After the array rebuilt, gnome-disk-utility reported the total number of components in the array as "3" and the status of the array as "Running". Everything is as expected so far.
c. Removed a component from the array using the Edit Components GUI. The selected component is removed from the array. gnome-disk-utility continues to report the total number of components in the array as "3" and reports the array status as "degraded".
d. Attempts to stop and restart the array using the GUI did not resolve the problem. The array continued to report its status as "degraded" and the number of components as "3" even though there were only two components. While in this state, any component added as a "spare" using the GUI was immediately brought into service and the array rebuilds with 3 components.

Note: If, in step b., I select "Add Spare", select the new component, then remove one of the old components, gnome-disk-utility reports the array as degraded, rebuilds into the spare, and when done, reports the status as "running" and the number of components in the array as "2". This is desired behavior, but does not address my problem.

I wish to always maintain at least two healthy disks in my array. If I need to replace a disk with a new one, I can, as mentioned in the note above, mark the new disk as a spare and remove the old disk from the array. While this will eventually rebuild the array, it leaves the array in a degraded state until the new disk is fully synced, leaving data at risk. Rather, I wish to be able to add a new disk to the existing array of two disks, have it sync up, then remove one of the old disks, leaving one old and one new disk in the array. In this situation, there are always at least two disks in the array at all times. Unfortunately, this does not result in the desired result, as gnome-disk-utility thinks that I want to permanently change the number of disks in the array from 2 to 3. There is no way to tell gnome-disk-utility that I wish to decrease the number of disks in the array from 3 to 2.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: gnome-disk-utility 2.30.1-1
ProcVersionSignature: Ubuntu 2.6.32-21.32-generic 2.6.32.11+drm33.2
Uname: Linux 2.6.32-21-generic i686
NonfreeKernelModules: nvidia
Architecture: i386
Date: Fri May 7 00:45:27 2010
InstallationMedia: Ubuntu 9.10 "Karmic Koala" - Release i386 (20091028.5)
ProcEnviron:
 LANG=en_US.utf8
 SHELL=/bin/bash
SourcePackage: gnome-disk-utility