X-RAID vs. 2xRAID-1

StephenB wrote:
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).

But scenarios you mentioned (and other you didn't) apply to disks regardless of the NAS configuration. They're not an argument for or against xraid or 2xRAID-1. When spike happens I can loose the whole NAS, be it xraid or raid-1, and - I agree - the additional backup is the only remedy.

StephenB wrote:
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.

I was planning to do it anyway. The problem I have is which NAS configuration to choose. I was thinking 2xraid-1 could be a bit safier because when one drive fails, I'll have another one with data (other scenarios aside). At the end of a day I'll have data on vol. 1, 1:1 copy on vol. 2 and a backup on a usb drive. Or am I completely mistaken?
What does xraid do to the second drive, how does this protection work? How is data stored on it; can I retrieve it from the second driveit e.g. by connecting it in a PC and mounting in Linux?

StephenB wrote:
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.

The whole thing with NAS and backup is because I lost all my data due to a disk failure (yes, I'm one of those that start doing backup after a disaster). I've still got it and hope one day I'll be able to recover it (it's extremely expensive here in Poland). At the same time I'm trying to protect againt another accident.
By syncing I ment what you wrote, it was only shorthand for all those operations.