2017-04-24 14:37 GMT+02:00, Andreas Klauer [off-list ref]:

On Mon, Apr 24, 2017 at 02:13:24PM +0200, Patrik Dahlström wrote:

quoted

I'm afraid it doesn't say that.

You said you found an ext header in the raw data.

Yes, I found ext headers in both /dev/sda and /dev/sdf, but it doesn't
show up in the 6 disk raid (/dev/md1).

If that exists then only thing I can think of is that you ended
up picking the wrong offset (or disk order) after all.

What offset are you referring to here? The --data-offset to the mdadm
--create command?

quoted

I do know that both raids contains only zeros for
many MB before any data appears.

This could be normal for the 5disk array since that part already
reshaped and the offset changed and there just could happen to
be zeroes somewhere in the beginning of a filesystem after the
first block of metadata.

Makes sense

Basically the 5disk array is supposed to have bogus data at
the start in your case. But it should turn into valid data
at whatever point the reshape did not yet reach.

Should I then be able to find a copy of ext4 superblock in the 5 disk
array once valid data start to appear?

This bogus data makes it hard to determine the correct offset
but according to the output you showed before the offset should
be 128M here.

I found out that there existed a ext4 file system at offset 0x7B80000
(123,5 MB) on both /dev/sda and /dev/sdb. I will adjust my mdadm
--create commands to this offset when I get home and try again.

For the 6disk array you should see valid data (starting with
the filesystem header) for however far the reshape was already done.
Depending on how the filesystem works you might even be able to
mount it but everything that is located behind the progress point
would appear corrupted.

Interesting. Like I said above, I will retry the create commands with
123.5 MB --data-offset.

Again if one of the disks actually was kicked from the array
while the grow was going on, you should leave that disk out as missing
as otherwise it will just appear as wrong data in both arrays.

I don't think the disk was ever kicked out. The kernel reset the link
and continued, I believe.

Regards
Andreas Klauer

Best regards
Patrik Dahlström