====== FreeNAS - Pool - Migrate a RAID-Z1 vdev to a RAID-Z2 ======

The easiest method is to set up a second FreeNAS which is setup with a RAID-Z2 and copy everything to it.

However if that is not possible, following steps can be taken.

<WRAP info>
**NOTE**:  Assumption is that:

  * **TANK**: is the primary dataset name.
  * **TEMP-TANK**: is the name for the new pool prior to data migration.

The steps are:

  * Replicate from TANK to TEMP-TANK.
  * Remove (or rename) TANK.
  * Rename TEMP-TANK to TANK.

In essence this means:

  * Copy the data off the pool using ZFS to preserve all the file permissions and everything.
  * Destroy and recreate the vDev and pool.
  * Move everything back as it was.

</WRAP>

----

===== Save the System Configuration =====

Take a backup of the system configuration.

Navigate to **System**.

  * Select the **General** tab.
  * Click **Save Config**.

{{:freenas:pool:freenas_-_system_-_general_-_save_config.png?800|}}


<WRAP info>
**NOTE:**  This backup will be needed later, because when TANK is detached, this will lose any share, snapshot and replication settings.
</WRAP>


----

===== Move the System Dataset =====

The system dataset needs to be moved off of TANK.

Use the GUI to select a new location other than TANK or TEMP-TANK.

Plug a USB drive into a free USB port.

Navigate to **Storage -> Pools**.

  * Click **Add** to create a new pool.

<WRAP info>
**NOTE:**  The name does not matter.

In this example, it is called sysbackup.
</WRAP>


After the new pool is created

Navigate to **System -> System Dataset**.

  * System dataset pool:  **Select the new pool**.
  * Syslog:  **Checked**.
  * Reporting Database:  **Not Checked**.
  * Click **Save**.

<WRAP info>
**NOTE:**  After a while, the System Dataset will be on the new pool.
</WRAP>

----

===== Create the Backup Pool =====

Navigate to **Storage -> Pools**.

  * Click **Add** to create a new pool.

<WRAP info>
**NOTE:**  The name does not matter.

In this example, it is called backup.
</WRAP>

----

===== Backup the Data Pool =====

Create a snapshot of the root dataset on the pool to backup.

Navigate to **Storage -> Pools**.

  * Select your root dataset.
  * Click the 3 dots.
  * Select **Create Snapshot** at the bottom.
    * Name:  **A simple name**.  In this example the name **migrate** is used.
    * Recursive:  **Checked**.

<WRAP info>
**NOTE:**  An alternate method to take a snapshot is through the CLI.

Open an SSH session to your FreeNAS box as root.

<code bash>
zfs snapshot -r tank@migrate
zfs send -R tank@migrate | zfs receive -F backup
</code>

  * **tank**:  the name of the volume being backed up.
  * **migrate**:  the name of the snapshot.
  * **-F**:  allows overwriting the existing pool that FreeNAS created when you created the backup pool.
  * **backup**:  The new pool created earlier.

This takes a very long time, often hours.

It is recommended to keep the SSH session open until the command completes

It does not give you any info on the progress of the command, but you can check how much data has been written through the normal reports in the Web GUI.

</WRAP>

----

===== Verify that all the data has been successfully backed up =====

All the data should be on the backup pool.

<WRAP alert>
**IMPORTANT:**  Verify this before continuing.
</WRAP>

----

===== Destroy and Remake the Data Pool =====

===== Detach the old pool =====

Navigate to **Storage -> Pools**.

  * Select the old pool (in this case tank).
  * Click the 3 dots.
  * Select **Detach** at the bottom.
  * Select **Destroy**, and do not delete the shares.
  * Click **Save**.

<WRAP alert>
**ALERT:**  This will completely delete all you data on the pool with no chance of recovery!

It is highly recommended that in addition of the backup pool just created, that another copy of the data is saved elsewhere.

The pool only needs to be destroyed if some of the old drives will be reused.

</WRAP>

----

===== Create the replacement pool =====

Pull the old drives, and replace with different drives if needed.

Creating the new pool tank as a RAID-Z2 vdev.

Navigate to **Storage -> Pools**.

  * Select **Add**.

<WRAP info>
**NOTE:**  Ensure this is named the same when you recreate it.
</WRAP>

----

===== Move the Data Back =====

SSH in.

Run the copy command in reverse.

<code bash>
zfs send -R backup@migrate | zfs receive -F tank
</code>

<WRAP info>
**NOTE:**  This may take a very long time, often hours.
</WRAP>

----

===== Export and Import the New Pool =====

In the GUI.

Navigate to **Storage -> Pools**.

  * Select the new tank
  * Select Detach.


<WRAP info>
**NOTE:**  Do not select **destroy** this time!

By releasing the tank, and importing it again, will result in the pool being **re-inventored**.

</WRAP>

  * Select **Import Volume**
  * Import tank again!

----

===== Restore the system dataset =====

Move the system dataset back to the main pool.

<WRAP info>
**NOTE:**  If the system drive was used for this backup instead of a separate USB drive, you can skip the detachment steps below.
</WRAP>


The steps are exactly the same as in step 2, just select tank instead.

Navigate to **System -> System Dataset**.

  * System dataset pool:  **Select the new pool**.
  * Syslog:  **Checked**.
  * Reporting Database:  **Not Checked**.
  * Click **Save**.

<WRAP info>
**NOTE:**  After a while, the System Dataset will be on the new pool.

</WRAP>

----

===== Detach the sysbackup pool =====

After the system dataset is moved back, detach the sysbackup pool, no need to destroy it, and remove the USB flash drive.

<WRAP info>
**NOTE:**  Everything should be fine.

If not then restore the system configuration.

  * The process is the same as in step 1, you just need to select Upload Config instead.
  * The system will reboots two times, and everything should be back to normal.

</WRAP>

----