Backup Question / Transform Stripe into Mirror Setup

My current setup is like this:
TrueNAS-SCALE- (TrueNAS SCALE Dragonfish [release])
With 2 8TB HDD set in Raid 0 (Stripe Mode)

When I set the system up I started with 1 HDD, copyd the data from the First HDD to the second and then included the Second in the Stripe Mode.

Now I want to make Backups of the Files and from what I understand so far replication task requires a Source that’s big enough to contain all files. Sadly I have a bit over 3TB of files and my biggest external drive is 2TB so I don’t think I can make a full backup like this and Cloud services are too expensive.

Are there other Backup ways/ tool to allow me making a backup that fits onto my 2TB HDD?
Also would it be possible for TrueNAS Scale to turn off and on my external Hard Drive so it’s only turned on for Backups? Or would I need a Second TrueNAS Setup for that?

If not I would like to break up my Raid 0 and convert it into a Raid 1 (Mirror).

Is it possible to archive this without needing to copy all my data to multiple drives? In theory all files should fit without a problem into 1 HDD.

Thanks for any help!

You should be able to remove one of the vdevs, and then when that finishes, extend the remaiming vdev with the now removed disk.

The issue is that if you have a disk issue while this disk heavy operation is happening you’ll lose everything.

So, that’s why people suggest backing up.

So, backup the most important content to your largest drive. And then the rest of the content to other places, random pcs, etc.

You probably won’t need the backup anyway. But if you do then you will want it.

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Thanks for the detailed answer!
Hmm now I need to debate if I just want to buy an 8TB external HDD as a backup next month or do it the way you descriped including backing up my data.

So there is no way of making a backup that zips the data to make it smaller?

Depends on the data.

Thing is, by default ZFS already uses compression. It’s not very strong. But it’s already compressed, so it depends on how you’re figuring your disk size.

Btw, fwiw, you should probably get the 3rd 8TB then setup a raidz1 with 3 8TB drives.

For the same available as you have now.

AND you can do this fairly safely.

Backup your current pool to the new drive.

Then build a degraded 3 disks raidz1 (this is a technical thing) with the existing disks.

Then restore from the backup.

Then replace the degraded disks with the 3rd disk.

Problem is that my HP Elitedesk 800 G4 SFF only has 2HDD slots. So I would need either an 8TB SSD (expensive) or an external 8TB HDD.

Would you suggest building a raidz1 with an external HDD?

And can you also do that without destroying the pool or would I then need to make a full backup on another external drive and redo everything?

So not very suitable for use as a NAS.
Get an external drive that is large enough for the backup. Then proceed according to the second post: Detach a drive from the GUI, and when it’s done extend the remaining vdev with it.

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