fsck of chiara backup disk (UUID="90a5c98a-22fb-4685-9c17-77ed07a5e000") was done. But this required many files to be fixed. So the backed-up files are not reliable now.
On the top of that, the disk became not recognized from the machine.
I went to the disk and disconnected the USB and then the power supply, which was/is connected to the UPS.
Then they are reconnected again. This made the disk came back as /media/90a5c98a-22fb-4685-9c17-77ed07a5e000. (*)
After unmounting this disk, I ran "sudo mount -a" to follow the way of mounting as fstab does.
Now I am running the backup script manually so that we can pretend to maintain a snapshot of the day at least.
(*) This is the same situation we found at the recovery from the power shutdown. So my hypothesis is that on Oct 16 at 7 AM during the backup there was a USB failure or disk failure or something which unmounted the disk. This caused some files got damaged. Also this caused the disk mounted as /media/90a5c98a-22fb-4685-9c17-77ed07a5e000. So since then, we did not have the backup.
Update (20:00): The disk connection failed again. I think this disk is no longer reliable.
sudo fsck -yV UUID="90a5c98a-22fb-4685-9c17-77ed07a5e000" [238/276]
[sudo] password for controls:
fsck from util-linux 2.20.1
[/sbin/fsck.ext4 (1) -- /media/40mBackup] fsck.ext4 -y /dev/sde1
e2fsck 1.42 (29-Nov-2011)
/dev/sde1 contains a file system with errors, check forced.
Pass 1: Checking inodes, blocks, and sizes
Error reading block 527433852 (Attempt to read block from filesystem resulted in
short read) while getting next inode from scan. Ignore error? yes