Question about how to migrate raid0 to raid5

[Zhang Jiejing <b33651@freescale.com>]

  Hi Neil Brown,

Sorry for interrupt you.

I'm using linux md raid0 in my server, and it's working very good unless 
it's outof space recently.
Thanks for you good job.

I have two question about linux md,
1. the first one maybe a common one:
     I install my server /home dir as RAID-0 for speed, this server is 
usually to code build and development, but recently I need add a 2TB HDD 
to this md, and I found add disk on RAID-0 is not supported, but I found 
there will maybe a way to convert my RAID-0 to RAID-5, and then add 
other disk on the RAID-5  (I don't covert it back).

I sow some patch about md takeover:
like
md/raid4: permit raid0 takeover
md: Fix dev_sectors on takeover from raid0 to raid4/5

But I'm a newbie about linux md, can you give a some guide about how to 
do this or it was not supported ?

My kernel version: Linux  2.6.38-15-server #64-Ubuntu SMP Fri Jul 6 
19:08:52 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

mdadm - v3.1.4 - 31st August 2010


2. the second question is about radi0.c : create_strip_zones() function,
this function will scan mddev->disks  and check them EQUAL size or not, 
can you give me some guide about where this disks passed to this mddev ?

The reason I ask this question is, I add a new HD, and partition two 
"Linux raid autodetect" partition on this disk, but I don't know how to 
add this disk to md1.

So I type:
  mdadm --add /dev/md1 /dev/sdc
and report -EINVAL error.

I first tough is I caused by my partition not right, so I partition my 
sdc to 2 partition, with partition type is "Linux raid autodetect".

and found also failed, so I did some google, and found RAID-0 don't 
support add disk online.

After did a ubuntu "do-release-upgrade", and reboot, I found kernel will 
check /dev/sdc, looking at sdc, and then failed to create the zone.

After remove the HD in BIOS, I can success mount the md1 again, so my 
question is do I need do some mdadm command to remove the /dev/sdc in my 
md1 (maybe it record the device node in some where ?)


Thanks for you advance.

-- 
BR,
Jiejing