On Wed, Sep 07, 2016 at 08:07:59PM +0200, Christoph Anton Mitterer wrote: > Even other multi-device containers (LVM, MD) don't at least corrupt > your data like it allegedly can happen with btrfs.
LVM and MD also check sequence numbers and timestamps. You can't just guess the UUID, you need a UUID *and* some other values that change every time an array is activated. They don't change enough for security purposes--it's still possible to intentionally spoof them--but they do prevent accidents like dd copies of hard drives or LVM snapshots. In this case, only one of the copies will increment its sequence number, and after that the other copies will not be permitted to join the array any more. BTRFS could use transids for this. It currently seems to accept the last device to present the desired device UUID without checking to see if the transid is consistent with the other devices, or if there are other devices with the correct UUID and transid. More can be done here.
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