Fantastic. I'm following!

The script takes the drives as arguments:

$ pwd
/usr/lib/systemd/system
$ cat drive_backup.service 
[Unit]
Description=backup fdisk + e2image
Wants=drive_backup.timer

[Service]
Type=oneshot
ExecStart=/usr/bin/backup_meta_data.sh /dev/sdc1 /dev/sdb1

[Install]
WantedBy=multi-user.target

Set to run at 3:40am every day, but probably could be once weekly really.

$ cat drive_backup.timer 
[Unit]
Description=timer to run drive backup
Requires=drive_backup.service

[Timer]
Unit=drive_backup.service
OnCalendar=*-*-* 03:40:00

[Install]
WantedBy=timers.target

Should be fairly self-explanatory.

$ cat /usr/bin/backup_meta_data.sh
#!/bin/bash

working_dir=/home/st/drive_recovery/working
backup_dir=/home/st/drive_recovery
backup_date=$(date +%Y%m%d-%H%M)

mkdir -p $working_dir

sudo fdisk -x > $working_dir/$backup_date.fdisk

for var in "$@"
do
	clean=$(echo $var | sed 's;/;-;g')
	sudo e2image $var $working_dir/$backup_date.$clean
done

sudo 7z a $backup_dir/$backup_date.archive $working_dir/"$backup_date"*
sudo rm $working_dir/"$backup_date"*

May I point out that all a RAID1 does is sync the blocks between two drives. It won't protect against writing something dumb that would mess up the filesystem, it will just dutifully sync it.

You should be able to back up ext data from a filesystem on a RAID array, unless I'm confused about what e2image actually does. Are you trying to use it on the underlying drive devices by any chance? You have to point it at the RAID device on top of them, something like /dev/md1 rather than /dev/sda1.

This sounds like a good extra backup to have but don't let it lull you into a false sense of security. It may help recover from a very specific kind of mistake but the recovery may be very specific as well. It's not file backup.

I'm really curious as to why go to all this trouble instead of using a proper file level backup and restore solution.

e2image

There's a good reason for the 2 in the name.

Today we have ext4, and ZFS of course.