Recovery on a RAID6/Gentoo/mdadm? Active drive is marked as spare.

Hallo

I am new to this group but I am desperate to find some hope or maybe
even an answer to a problem I have now for 3 days. I used to have a
700 GB RAID6 on a Gentoo Server (made with 7 HDDs) and sine it was a
RAID6, I figured I can put some data on it that is quite valuable like
my personal files folder. Guess this was stupid and I will probably
rather use a mirrored drive and to daily backups with backular or
rsync in the future, but this will not help me right now:
Some days ago, I lost one of the HDDs, which was more or less ok,
since I still had 6/5 so I postponed the purchase of a new HDD until
payday. The bad thing however happened and a second drive went offline
at the beginning of last week, probably due to the summer heat.

As I noticed this, I turned off the Server and bought a new HDD, put
it in and rebooted. I added it to the raid and it started recovering.

Now things started to go wrong: The PC crashed (lockup) at about 2% of
the recovery and I had to turn it off. Upon reboot, Only 3 drives
(plus the new one showed up in /proc/mdstat and the RAID would not
start. However I checked for the other drives of the array and they
where there (ls /dev/hd*) and also had a valid superblock (mdadm -E /
dev/hd*). The superblocks told me however, that 5 drives where in
"active sync", 2 where missing.

Now I probably made a big mistake and did (after trying mdadm --
assemble) a "mdadm --add /dev/md0 /dev/hd*" on one of the drives that
where for some reason not in the RAID. It was added as "spare" to the
RAID, not as a regular drive (so the Superblocks now told me there
where 5 drives in "active sync", one "spare" and two "missing"). I am
not sure if I did use --re-add or just --add, in any case it was bad.
Shortly after this, I recognized the problem with the missing drives
as a matter of faulty ATA-Controllers, since depending on which
controller a drive was plugged in, it was recognized by /proc/mdstat
or not upon reboot. So I got a really big SATA drive, plugged it in
and did subsequently a "dd if=/dev/hd*1 of=/mnt/satadrive/hd*1" to
make backups of the partitions of the RAID drives. I used only one at
a time on a working controller (and dumped the faulty controllers).
After a day of dd'ing, I did "losetup /dev/loop* /mnt/hd*1" on all the
5 partition mirrors and tried to assemble a RAID from it (mdadm --
assemble /dev/md0 /dev/loop1 /dev/loop2/ ...). It said "assemble from
4 drives and 1 spare" and did not start of course, since I need 5
drives.

I was getting desperate and tried a tool called mddump to show me the
superblocks of the partitions. As mdadm said, 4 drives where rather ok
(showing up as "active sync" in mdadm -E however) and one was maked as
spare. I made backups of the SBs and tried to modify the one of the
spare drive. There where 5 drives listed as ok, but only 4 drives
existed, one was just not there, so I put that drives device number
(and major/minor number) on the device claiming to be a spare and
tried to assemble the RAID again. This time, I got an "IO-Error" and
of course no RAID.

So I put the backups of the superblocks back and started to think
about ways to get the lost Data back from a couple of DVDs, CDs or
Memorysticks, where little bits of the data may still have had copies
(about 1-2% of the data).

I kept the partition backups and the original drives however in the
hope, I can find someone who can possibly help me and this is my
question to this group - does someone know what I can still try or is
there a certainty, that all data is lost?

Greetings, Anja