Cannot mount 'mypool': Input/output error

[Szycha]

Hardware: AMD Athlon II X2 270 with 8GB RAM (non-ECC) + Areca ARC-1231 in RAID 5 configuration 6x3TB drives. Created one volume.
System: FreeNAS-8.3.0-RELEASE-p1-x64 (r12825) (yes it's old, but unfortunately I am plagued by infinite reboot loop if I upgrade to a newer version)

At the time I was setting this up, I did not think to use JBOD (or pass-through mode) ... I just added one whole disk and made a zpool ....
Everything worked quite good, but one day when I was streaming from this server (via samba), stream has frozen and I ended up rebooting the NAS box.
After reboot, I could no longer see my volume in FreeNAS. I tried "Auto import Volume" function in GUI and then "zpool scrub mypool". This caused my areca to drop one drive "FAIL". I had to replace (lots of read errors). Rebuild was done and I went through the steps again. Than a second disk got rejected (also read errors). I replaced that drive as well and went through the rebuild. After that I verified volume and areca had no more complains. Thus back to the zpool. I can import it and I can see the status.
The state is ONLINE but I am unable to mount it because of resulting "Input/output error".

Here is what I get from #zpool status -v
pool: mypool
state: ONLINE
status: One or more devices has experienced an error resulting in data
corruption. Applications may be affected.
action: Restore the file in question if possible. Otherwise restore the
entire pool from backup.
see: http://www.sun.com/msg/ZFS-8000-8A
scan: scrub repaired 0 in 37h44m with 311903 errors on Thu Feb 26 20:13:50 2015
config:

NAME STATE READ WRITE CKSUM
mypool ONLINE 0 0 1
gptid/bxdbfxdb-4d1e-11x2-bed4-001x2127ax4a ONLINE 0 0 4

errors: Permanent errors have been detected in the following files:

mypool:<0x0>
mypoool:<0x3e002>
mypool:<0x3e005>
....
...
..
.
mypool:<0x3e7f4>


Here is my attempt to mount it.
#mount -t zfs mypool /mnt/mypool
#mount: mypool : Input/output error

I went through a full scrub (as you can see from the above status output), but it gave me no relief.

Is anyone able to help me with such problem or am I SOL?
Even if I get to parts of the data this would be great.

P.S.
No, I do not have a backup ... I planned it but never got to execute it.

 

[Bidule0hm]

Well, non ECC RAM = problems, hardware RAID controller in non passthrough mode = problems, so non ECC RAM + hardware RAID controller in non passthrough mode = more (infinite?) problems... (and very likely data loss in the short term).

I can't say anything more.

 

[cyberjock]

Well, you have zero redundancy with ZFS because you did a hardware RAID5. So you're data is gone for good unless you get really really lucky or are ready to pay $20k+ for recovery from a company like Ontrack.

Me personally, even if you offered to pay me to try to fix it, I wouldn't even take the offer.