Hi,

I have been testing TrueNAS for a couple of weeks, but after the demo tour of Unraid I believe it will fit my needs much better.

Current hardware

System
Intel Core i3-10100, 3.6 GHz, 4 cores / 8 threads
16 GB DDR4 (2×8 GB), 3600 MHz, CL16
512 GB NVMe SSD (PCIe 3.0 x4, M.2 2280)
Gigabyte B560M AORUS PRO motherboard

Drives
WD20EARS-00MVWB0, 2 TB, 5400 RPM (WD Green)
WD30EFRX-68AX9N0, 3 TB (WD Red NAS)
WD30EFRX-68EUZN0, 3 TB (WD Red NAS)
WD80EDAZ-11TA3A0, 8 TB (WD Red Plus / white label)
Gigabyte GP-GSM2NE3512GNTD, 512 GB NVMe SSD

I have also purchased a new empty disk to assist with the migration:

Seagate IronWolf ST8000VN004, 8 TB (NAS)

My assumption is that I first need to format the IronWolf with a filesystem that Unraid can read, then copy all data from TrueNAS to that disk (internal, not over network) before setting up the final Unraid configuration. It is very important that no files or metadata are lost during this process.

The goal in Unraid is to have two storage areas:

Mirrored secure storage
WD30EFRX-68AX9N0, 3 TB (WD Red NAS)
WD30EFRX-68EUZN0, 3 TB (WD Red NAS)

Large non-mirrored (raid) storage area where I can add disks later, and where a failed disk only affects the data stored on that specific disk:

WD20EARS-00MVWB0, 2 TB (WD Green)
WD80EDAZ-11TA3A0, 8 TB (WD Red Plus / white label)
Seagate IronWolf ST8000VN004, 8 TB (NAS)

What would be the safest and most reliable way to perform this migration?

Can you add another 512G nvme? I would mirror that and put all HDD in the parity array.

Yes, I can buy another NVMe. It will probably have to be a 1 TB model if I cannot find a reasonably priced 512 GB, but that should not matter. It may take a little time before I receive the disk, but from what I understand it should be possible to add it later and convert the cache to a mirror without any issues.

Your suggestion about using parity for the entire HDD array is reasonable. The downside is that I would lose quite a bit of usable space since one of the 8 TB drives would need to be used as parity. While it is certainly nice to have all data protected, in my case only about 1 TB of the data is truly irreplaceable, and that part will also be backed up to Backblaze. That said, I do understand the appeal of having one single protected storage pool for everything.

In any case, since the initial copy to the 8 TB migration disk will likely take 10 to 15 hours, I would like to start that process as soon as possible. What would be the safest way to prepare the disk and transfer the data? Should I move the drive to a Windows computer and format it as exFAT, or can everything be done directly in TrueNAS where the disk is currently installed so the transfer happens internally?

1 hour ago, Unrailed said:

downside is that I would lose quite a bit of usable space since one of the 8 TB drives would need to be used as parity

I assumed you were planning to have parity.

1 hour ago, Unrailed said:

1 TB model if I cannot find a reasonably priced 512 GB

That mirror would only have 512GB total capacity.

1 hour ago, Unrailed said:

Should I move the drive to a Windows computer and format it as exFAT,

I don't think Windows can do that natively and that is not the best approach anyway.

You must let Unraid format each disk it will use in the array, XFS is recommended.

You can transfer over the network (which I assume is what you had in mind when you were thinking Windows) to Unraid. Unassigned Devices plugin will let you mount remote shares and work with them directly on your Unraid server.

1 hour ago, Unrailed said:

While it is certainly nice to have all data protected, in my case only about 1 TB of the data is truly irreplaceable, and that part will also be backed up to Backblaze.

And parity or mirror is not a replacement for backup anyway. Plenty of much more common ways to lose data besides a failed disk, including user error.

Thanks, I understand that if I add a 1000 GB NVMe, only 512 GB will be usable when mirroring it with the existing 512 GB drive. I will try to find a 512 GB model, but if the price difference is small I may still buy a 1000 GB.

Regarding parity, I understand the concept but did not plan to use it initially. The main pool will therefore be unprotected. If a disk fails, the data on that specific disk will be lost, and I accept that. Sensitive data will instead be stored on two mirrored 3 TB drives and backed up to Backblaze. I may add a parity disk later, but it feels too expensive right now since I just bought an 8 TB disk for the migration.

I would also like to avoid copying files over the network to speed things up, which is one of the reasons I bought the 8 TB backup disk. After some reading it seems that exFAT might be the best filesystem since it is supported by Windows, TrueNAS and Unraid. NTFS is another option, but Linux support does not seem as good, if I understood correctly. If I choose exFAT I will have to mount the 8 TB backup disk in to a Windows 11 computer to format it. If I manage to set up the 8 TB backup disk properly, I could copy everything from TrueNAS to it and then transfer the data to Unraid after installation and pool creation without using the network.

However, in my current TrueNAS SCALE setup only the two 3 TB drives are in RAID (mirrored). All other drives have their own pools and datasets. This is not the typical TrueNAS setup, but in my case most of the data is replaceable.

Both Unraid and TrueNAS support ZFS if I understand correctly. Since most of my disks are not in RAID, I should be able to export them (except for the mirrored pair) and then import them in Unraid. During the Unraid installation I would only use the NVMe drive, then add the 8 TB backup disk as a JBOD disk without parity and move the data there. Once the data from a ZFS drive has been moved, that disk could then be added to the JBOD pool together with the 8 TB disk.

Is this approach possible, and how big is the risk that something fails during the process?

The version of TrueNAS I got is 25.10.2.1 - Goldeye if that helps. The Disk pools looks like this:

Edited March 15Mar 15 by Unrailed

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/file-systems/#ntfs-and-exfat-limited-support

That would be a way to get started with the new 8TB already full of data, but when you free up other drives I recommend XFS for the array, and eventually converting (reformatting) that original 8TB to XFS also.

Thanks, I found this link: Version 7.1.0 2025-05-05 | Unraid Docs

So I booted Unraid, mounted the ZFS disk and verified that I could read the files without any problems.

The new 8 TB backup disk was then added to the array and formatted with XFS. After that I created a script that copies all data to the 8 TB disk.

The copy process has now been running for about 10 hours and is currently at 63%. The speed is not very high, around 70 to 80 MB/s, probably because rsync verifies the files during the transfer and because the data is being copied from ZFS to XFS.

Here is the script I am running:

set -e
mkdir -p /mnt/disk1/data1
mkdir -p /mnt/disk1/data2
mkdir -p /mnt/disk1/data3_secure
mkdir -p /mnt/disk1/data2/ix-apps
rsync -aHAXS --numeric-ids --info=progress2 /data1/ /mnt/disk1/data1/
rsync -aHAXS --numeric-ids --info=progress2 /data2/ /mnt/disk1/data2/
rsync -aHAXS --numeric-ids --info=progress2 /.ix-apps/ /mnt/disk1/data2/ix-apps/
rsync -aHAXS --numeric-ids --info=progress2 /data3_secure/ /mnt/disk1/data3_secure/
sync

54 minutes ago, Unrailed said:

70 to 80 MB/s

I assume this is without parity.

Yes, that’s correct. I only added the 8 TB backup disk and formatted it as XFS. The problem is that the terminal session keeps closing from time to time. It has now happened twice, which stops the copy process.

I might need to use tmux so the operation continues running on the server even if the terminal disconnects, but tmux is not installed by default. Since I have not added the cache drive yet, it seems that some apps cannot be installed.

Right now it is a bit confusing how I should copy the remaining files in a reliable way without the process stopping when the terminal closes.

As long as you have any storage you can install apps, but it's better if you don't enable Docker or VM Manager until you have cache.

As far as I know, you can install any plugin whether or not you have storage, though some plugins don't have much use without storage.

You can definitely install Tmux Terminal Manager plugin now.