Mdadm/ZFS RAID question

[Petter Adsen]

I have a 3TB disk with a lot of data that I would like to put in a RAID
for a little extra security. What I'm wondering is: is it possible to
buy a new disk, set up that disk as a degraded RAID, populate it with
data and then add the old disk to the mirror and have it synced from
the new disk?

Can either ZFS or mdadm do this, or will I need another disk to hold
the data and set up the whole mirror at once? I know btrfs can do this,
but I don't quite trust it with that particular set of data.

Petter

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