I can think of 2 reasons why those files cannot be read:
1) The power outage destroyed them.
2) The files are stored in a way (fragmented, or some special inode) that the implementation of the filesystem in UFS-explorer can't decode it.
In case 1 you could, depending on the nature of the data, try to use PhotoRec
to recover them. But I don't know if it will be easy to find those 10 files between the 20000 other ones, as it is perfectly possible that PhotoRec can recover the files, but not their names.
In case 2 you could boot your PC from a Linux Live CD or -USBstick
, and use it to read the disk. (Linux has native support for XFS, it is also the OS of almost every NAS).
Theoretically you could also use your 2Big2 for it, by connecting a disk to the eSata- or USB port, but unfortunately the half RAID1 partition will not be automounted, so you'll first have to hack the 2Big2 to get shell access, and to mount the partition manually.
With a live CD you'll have to mount it manually too, BTW, but getting a shell is much easier.
It is not useful to put the 2Big disks in a 2Big2. The OS is on the disk, and it's not compatible, so the 2Big2 won't even boot. (BTW, maybe another 2Big wouldn't boot either, because Lacie did something disgusting with partition identifiers)
When you want to connect the disk to a (Ubuntu) Live CD, use the following commands in a shell (terminal, command prompt) (assuming that the Lacie disk is the 2nd harddisk):
# create mountpoint
# mount the partition
sudo mount -t xfs -o ro /dev/sdb2 /tmp/mountpoint
If this works, you can use the GUI to find your files in /tmp/mountpoint. If it doesn't work, you'll have to assemble the raidarray first (you'll need internet access):
sudo apt-get update
sudo apt-get install mdadm
sudo mdadm --assemble /dev/md0 /dev/sdb2 --run
sudo mount -t xfs -o ro /dev/md0 /tmp/mountpoint