DANGER!!! Problems with 10.04 installer (RAID devices *will* get corrupted)

[Tom H]

On Wed, Apr 21, 2010 at 7:58 AM, Karl Larsen <klarsen1 at gmail.com> wrote:
> On 04/20/2010 10:30 PM, Alvin Thompson wrote:
>
>> Suppose you have a hard drive with some partitions on it.  On one of
>> those partitions you have a linux file system which houses your data.
>> We'll say for the sake of this discussion that sda2 contains an EXT4
>> file system with your data.  So far, so good.
>>
>> Because this data is too important to rely on a single drive, you decide
>> to buy some more drives and make a RAID 5 device. You buy 3 more drives
>> and create similar partitions an them (say, sdb2, sdc2, and sdd2). You
>> copy the data currently on sda2 somewhere safe, then you use mdadm to
>> create a RAID5 array with sda2, sdb2, sdc2, and sdd2. The new RAID
>> device is md0. You create an XFS file system on md0 and move your data
>> to it*. This is all perfectly fine, but the stage has been set for
>> disaster with the ubuntu installer.
>>
>> Later, you decide to do a clean install of ubuntu on sda1 (sda1 is *not*
>> part of the RAID array), and you get to the partitioning stage and
>> select manual partitioning. This is where things get really ugly really
>> fast.
>>
> Let me suggest this:
>
> 1. Go back to one hard drive.
> 2. Back up your important data. I use rsync and it works fine.
> 3. Now load 10.04 and it should be fine.
> 4. Your raid5 problems are typical.

RAID works perfectly well on 100s of 1000s (at the very least!) of servers.

The OPs point is that he thinks that he has uncovered a bug in the
installer whereby is makes a mess of partitions that are mdadm'd if
you install Ubuntu on a partition on one of the HDs that has one or
more partitions in the array. (IIRC the first time that the OP emailed
the list, he was using mdadm in both installs but I may be
misremembering).