I don't see why having the OS on disk lowers the usefulness as backup device. When the disk fails, your backup is gone anyway, no matter if the NAS still boots.
Is it possible to re load the operating system without having to resort to loads of other PC's some of which must use some form of Linux operating system ?
<nitpicker-modus>Yes. You can do it with only a single Linux PC using this directions
, where you skip step 'Data Partition
' to preserve your data.</nitpicker-modus>
If you can find uploaded partitions for some mirroring tools, it might be possible to restore the OS from a Windows machine, but in that case you'll loose your data, I guess. (And I'm not sure if it will work. Some crucial data is stored outside
the partitioned space. The mirroring tool might choke on that.
The data partition has an XFS filesystem. The only Windows tool which can read that where I'm aware of is XFS explorer.