as mentioned above, I've rebooted the drive with commented out /dev/md3 (/var) partition. It didn't boot obviously. I thought it would be simple. Connect the drive to a linux box, access /etc/fstab, remove the comment #, save the file, put the drive back in case and start it. Well, no luck.
When I tried to mount the drive, I used gparted at some point. It listed all my partitions as /dev/sda1 (fstab was there), /dev/sda2 (that's swap), /dev/sda3 (this is /var) /dev/sda4 (my data). All of them had raid flag on. I disabled the raid flag for /dev/sda1, mounted the drive as ext3, edited fstab, saved it and enabled the raid flag again. The drive is still not booting. I can hear it's powering on, but no blue lights, no nothing.
I haven't deleted any files on it. Editing fstab and temporarily disabling that raid flag was the only thing. My only guess is that raid setup is corrupt. Anyone know how to set it up properly? Any other ideas? I hope there's no need recovering it from scratch..