X-RAID vs. 2xRAID-1

Jarkod wrote:
...If I create a backup job and will have the same data on both disks, isn't it enough to protect against disk failure or data loss?

Disks-perhaps. Though identical disks in the same chassis can fail at close to the same time. Data loss - definitely not. There are plenty of scenarios that destroy both volumes. Power spikes and software bugs that corrupt the file system are two. Then there's disaster (flood, fire, theft, etc).

Jarkod wrote:

The point is I'd like to use it for both: a Lightroom folder with photos accesible from different computers and a backup of users' home catalogues. My thinking was to move a Lightroom folder with photos to vol 1 and make a backup home of calogues also on vol 1. Then make a copy of vol 1 on vol 2 and this way I'd kill two birds with one stone. But you're saying it's not enough. What happens to a drive/data when the other drive fails (in 2xRAID-1 configuration)? I thought it stays ok, data is safe and I can insert a new drive and manually sync it with the old one.

Again, drives are not the only thing that can fail. You will find regular posts here from people who assumed otherwise, and are desperately trying to recover their data. Such recovery might be a bit tricky with the new OS6 systems, since btrfs isn't as widely used at present as ext.

Most users are using the NAS for both purposes. The safest approach is to combine xraid with backup to another device. Your alternative to xraid is workable, and gives you some more space (since you only replicate the primary storage). But in my view it would be better if you backed up to a different system - or at least a usb/esata drive - that you removed after the backup was finished.

Personally I am conservative on backups - losing data years ago made me that way.

BTW, with jbod there is no syncing. You'd insert a new drive, re-create the shares, and restore them from backup.