Interesting: RAID1 two USB drives

[tigerten]

I always wanted to make backups of my NAS to two USB drives, to sync the two drives has not been ideal. I discovered this: 

chironFS, an very old and long discontinued filesystem. The newest version is 1.1.1 in 2008. However it still works. Here is how I got it working with Readyns with amd64 CPUs (no arms packages, unless someone can compile one). 

https://code.google.com/archive/p/chironfs/downloads

Install FUSE package and the chironFS ubuntu package. 

create a share "virtual" within UGI. 

Add this (modify to your case) to /etc/fstab: 

chironfs#/media/USB_FLASH_3=/media/USB_FLASH_1 /data/virtual fuse allow_other,log=/var/log/chironfs.log 0 0

restart ReadyNAS. 

you should be able to access share "virtual" . Adding or deleting file within "virtual" will simultaneously add and delete files on the two USB drives. 

Don't modify USB drive content directly. 

I think that is it.