Recover RAID6 with 4 disks removed

[Nicolas Karolak <nicolas.karolak@ubicast.eu>]

Hello,
I have (had...) a RAID6 array with 8 disks and tried to remove 4 disks
from it, and obviously i messed up. Here is the commands i issued (i
do not have the output of them):

```
mdadm --manage /dev/md1 --fail /dev/sdh
mdadm --manage /dev/md1 --fail /dev/sdg
mdadm --detail /dev/md1
cat /proc/mdstat
mdadm --manage /dev/md1 --fail /dev/sdf
mdadm --manage /dev/md1 --fail /dev/sde
mdadm --detail /dev/md1
cat /proc/mdstat
mdadm --manage /dev/md1 --remove /dev/sdh
mdadm --manage /dev/md1 --remove /dev/sdg
mdadm --manage /dev/md1 --remove /dev/sde
mdadm --manage /dev/md1 --remove /dev/sdf
mdadm --detail /dev/md1
cat /proc/mdstat
mdadm --grow /dev/md1 --raid-devices=4
mdadm --grow /dev/md1 --array-size 7780316160  # from here it start
going wrong on the system
```

I began to have "inpout/output" error, `ls` or `cat` or almost every
command was not working (something like "/usr/sbin/ls not found").
`mdadm` command was still working, so i did that:

```
mdadm --manage /dev/md1 --re-add /dev/sde
mdadm --manage /dev/md1 --re-add /dev/sdf
mdadm --manage /dev/md1 --re-add /dev/sdg
mdadm --manage /dev/md1 --re-add /dev/sdh
mdadm --grow /dev/md1 --raid-devices=8
```

The disks were re-added, but as "spares". After that i powered down
the server and made backup of the disks with `dd`.

Is there any hope to retrieve the data? If yes, then how?

Any help is really appreciated. Thanks in advance.

Regards,
Nicolas KAROLAK