XigmaNAS

6 2TB, each one from different batch. One drive failed, taken off line, replaced and started resilvering. During the re-silvering power went out and once ups was drained. everything went down.
Once I got home I have found the system completely off and unresponsive. It turns out it is a system board (with integrated atom cpu).
replaced board and restarted system and found the new drive as well as one additional drive are dead.
with zpool not being exported I can't import it but is there any tricks in zfs cookbook that i've missed while google-ing or I am out of luck?
Most of the data I have on external drive except for last couple years worth of pictures and videos.

Thanks sin advance.

so you had 1 drive fail and then another before the resilver finished.

if you have a raidz1 then your data is gone. in raidz2 you might have a chance.
zfs does not have any data recovery tools because its enterprise. the reasoning behind that is that if the pool is in such a state its best to restore it from backup.

From both of your posts I read that you had already several power outages which killed thedrives. So a UPS would be more than suitable in the future.

I would also run another off site backup server for all the crucial data.
On top of the Mirror redundancy in my NAS I am running BTSync with my little "Pi" and make a daily copy of the most important data.
It is very cheap and efficient way of keeping your data relatively safe (I have had to use it twice).
Little "Pi" with an external Ext4 formatted USB HDD does the job flawlessly and gives you a peace of mind.
I am also running a passive UPS, but that is only to wind the server down while power goes out, I had a power cut 2 days ago and UPS saved me a lot of work.

By the way I read that the UPS was drained?
Didn't you setup to wind the server down in settings once it goes on UPS or the batter on the UPS goes low?