What happen to data when adding a second disk?

Hello Community,

I was using my NAS with just one disk inside formatted in JBOD.
Having bought a new disk (same model and size as first one), I wonder what will happen to data (photos, videos,…) on first disk when I will plug the new one to free slot. I plan to make a RAID1 configuration.
Any idea? Should I backup every thing first or is it 100% safe?

I would definitely backup your data. My understanding is that whenever you change the raid configuration the disks are formatted. Perhaps someone here can confirm that.

Many thanks for your reply.
I do have backed up important personal files but I am lazy for remaining ones…
Anyway a regular backup on another storage device would be wise…

Meanwhile I asked question to WD support, I will share answer if any.

Just had feedback from WD support… All data will be wiped!
Be warned!

Yes but doing another JBOD wont. If its NAS certified dont do raid. Unless its so official materials costing you fortune if you loose it.

Indeed the question is worth being discussed as I am going to backup data on an external device.
In that case a RAID1 configuration is maybe a bit too much. Actually it also depends of the regularity of these external backups.
Thank you for your input, I have to think about it.

RAID 1 is not a backup; it’s a fault-tolerance method for data protection. The volume itself can still get corrupted and the RAID controller can fail. As such, a backup (A secondary copy available at the same time in a separate, independent location) is still recommended.

I doubt it. RAID 1 hardly fails. As its double copy of the data inside 2 hdd. So if either fails which fails RAID 1 still 1 hdd activate enough to retrieve the data. or rebuild the data.

Even if the raid corrupted it can be rebuild by inserting the new hdd or so.

There are two possibile options with RAID 1:

  1. Switch to RAID 1
  2. Migrate to RAID 1

what are the meaning?