Safest way to migrate data from Mirror to RaidZ1?

TrueNAS General
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Hello,

I have currently have a mirror pool of 2 disks and recently bought a new disk for my pool. I thought that I could convert my mirror into a RaidZ1 since I only add 1 disk but apparently NOT. So I need to delete my current pool to do it.

I do have a disk of 4To in my windows PC but how can I safely put ALL pool data on it then put it on the newly created pool WITHOUT losing any data.

I’m on 25.04.2.1.

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I don’t understand your setup or that you mean by

but you could do this slightly risky thing:

  • remove one drive from the mirror
  • create with at least 3 disks a RAIDZ1
  • copy the data from the mirror to the RAIDZ1

Not that I would recommend using RAIDZ1 or removing a drive from a mirror.
IMHO your best bet would probably be to buy another drive again and create a 4 wide mirror by adding these two drives to your current pool.

3

Please give us details on your current system and drives. The more details, the better the advice. We don’t know how much data you have on the TrueNAS system nor how many disk ports.

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  • Pool 1 : 2x Ironwolf Pro 4TB - Mirror

Currently using 3.80TB of data inside my pool

I bought a new Ironwolf Pro 4TB and plan to upgrade it to a RaidZ1.

Usable data from 4TB to 8TB and 1 spare.

How can I can not lose my data. Like I said I have a 4TB Toshiba disk where I can temporarily put data from the pool on it. How can I migrate data to this Toshiba without losing it or messing up the datasets?

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The spare bieng the Toshiba, I suppose?

Since you have four drives, and want to end up with three, there are some ways.

  1. Plug in the new IWP and the Toshiba.
  2. Logically remove one drive from your mirror, in the GUI. (data at risk…)
  3. Create a raidz1 pool with the new drive, the Toshiba and the drive you removed.
  4. Replicate your data to the new pool.
  5. Rename the pool to the same name as the old pool, and remove the read-only flag left by replication.
  6. Optionally, replace the Toshiba by the last drive from your old pool. (Or just leave it as it is and use this old IWP as spare.)

Other ways may involve the CLI and a degraded raidz1.

1 Like
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Wouldn’t creating a RaidZ1 with the toshiba restrain my other drives since the Ironwolf are more efficient?

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I doubt it would make a difference, but as outlined above you can still replace the Toshiba afterwards if you prefer to keep it as spare.
Or extend your mirror with the Toshiba now, and then remove the two IWP.

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Can I create the RaidZ1 with 2 disks and then add the new disk after I copy everything?

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Yes, but then the creation process involves the CLI. Search the forum for details: A convenient shorthand for relevant posts is “Here be Dragons”.

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Thank you for this. I had almost the exact same question, right down to the same IWP drive setup (going from 2x4TB to 3x4TB).

I should have just bought 3 to begin with, but I hadn’t yet convinced my finance office/spouse of the value proposition of turning my gaming desktop into a TrueNAS box.