Managing Pools

The Storage Dashboard widgets provide enhanced storage provisioning capabilities and access to pool management options to keep the pool and disks healthy, upgrade pools and VDEVs, open datasets, snapshots, data protection screens, and manage S.M.A.R.T. tests. This article provides instructions on pool management functions available in the TrueNAS UI.

Select Storage on the main navigation panel to open the Storage Dashboard. Locate the ZFS Health widget for the pool, then click the Edit Auto TRIM. The Pool Options for poolname dialog opens.

Select Auto TRIM.

Click Save.

With Auto TRIM selected and active, TrueNAS periodically checks the pool disks for storage blocks it can reclaim. Auto TRIM can impact pool performance, so the default setting is disabled.

For more details about TRIM in ZFS, see the autotrim property description in zpool.8.

Use the Export/Disconnect button to disconnect a pool and transfer drives to a new system where you can import the pool. It also lets you completely delete the pool and any data stored on it.

Click on Export/Disconnect on the Storage Dashboard.

A dialog displays showing any system services affected by exporting the pool, and options based on services configured on the system.

To delete the pool and erase all the data on the pool, select Destroy data on this pool. The pool name field displays at the bottom of the window. Type the pool name into this field. To export the pool, do not select this option.

Select Delete saved configurations from TrueNAS? to delete shares and saved configurations on this pool.

Select Confirm Export/Disconnect

Click Export/Disconnect. A confirmation dialog displays when the export/disconnect completes.

Upgrading a storage pool is typically not required unless the new OpenZFS feature flags are deemed necessary for required or improved system operation.

Do not do a pool-wide ZFS upgrade until you are ready to commit to this TrueNAS major version! You can not undo a pool upgrade, and you lose the ability to roll back to an earlier major version!

The Upgrade button displays on the Storage Dashboard for existing pools after an upgrade to a new TrueNAS major version that includes new OpenZFS feature flags. Newly created pools are always up to date with the OpenZFS feature flags available in the installed TrueNAS version.

Upgrading pools only takes a few seconds and is non-disruptive. However, the best practice is to upgrade a pool while it is not in heavy use. The upgrade process suspends I/O for a short period but is nearly instantaneous on a quiet pool.

It is not necessary to stop sharing services to upgrade the pool.

Use Scrub on the ZFS Health pool widget to start a pool data integrity check.

Click Scrub to open the Scrub Pool dialog. Select Confirm, then click Start Scrub.

If TrueNAS detects problems during the scrub operation, it either corrects them or generates an alert in the web interface.

By default, TrueNAS automatically checks every pool on a recurring scrub schedule.

The ZFS Health widget displays the state of the last scrub or disks in the pool. To view scheduled scrub tasks, click View all Scrub Tasks on the ZFS Health widget.

The Storage Dashboard screen Disks button and the Manage Disks button on the Disk Health widget both open the Disks screen.

Manage Devices on the Topology widget opens the Poolname Devices screen. To manage disks in a pool, click on the VDEV to expand it and show the disks in that VDEV. Click on a disk to see the devices widgets for that disk. You can take a disk offline, detach it, replace it, manage the SED encryption password, and perform other disk management tasks from this screen.

See Replacing Disks for more information on the Offline, Replace and Online options.

There are a few ways to increase the size of an existing pool:

• Add one or more drives to an existing RAIDZ VDEV.
• Add a new VDEV of the same type.
• Replace all existing disks in the VDEV with larger disks.

By default, a VDEV limits all disks to the usable capacity of the smallest attached device. If a pool is not automatically expanded, for example when resizing virtual disks in a hypervisor apart from TrueNAS, click Expand on the Storage Dashboard to manually increase the pool size to match all available disk space.

Extend a RAIDZ VDEV to add additional disks one at a time, expanding capacity incrementally. This is useful for small pools (typically with only one RAID-Z VDEV), where there is not enough hardware capacity to add a second VDEV, doubling the number of disks.

Overview and Considerations

TrueNAS 24.10 (Electric Eel) introduces RAIDZ extension to allow incremental expansion of an existing RAIDZ VDEV using one more disks. RAIDZ extension allows resource- or hardware-limited home lab and small enterprise users to expand storage capacity with lower upfront costs compared to traditional ZFS expansion methods.

To expand a RAIDZ array, TrueNAS reads data from the current disks and rewrites it onto the new configuration, including any additional disks.

Data redundancy is maintained. Make sure the pool is healthy before beginning the expansion process. If a disk fails mid-expansion, the process pauses until the RAIDZ virtual device (vdev) is healthy again, typically by replacing the failed disk and waiting for the system to rebuild.

The storage pool remains accessible throughout the expansion. If you reboot or export/import the pool, the expansion resumes from where it left off.

After the expansion, the extra space becomes available for use.

The fault-tolerance level of the RAIDZ array remains unchanged. For example, a four disk wide RAIDZ2 expanded to a six wide RAIDZ2 still cannot lose more than two disks at a time.

You can expand a RAIDZ vdev multiple times.

Existing data blocks retain their original data-to-parity ratio and block width, but spread across the larger set of disks. New data blocks adopt the new data-to-parity ratio and width. Because of this overhead, an extended RAIDZ VDEV can report a lower total capacity than a freshly created VDEV with the same number of disks.

Extended VDEVs recover lost headroom as existing data is read and rewritten to the new parity ratio. This can occur naturally over the lifetime of the pool as you modify or delete data. To manually recover capacity, simply replicate and rewrite the data to the extended pool.

You can use the RAIDZ Extension Calculator to visualize potential lost headroom and capacity available to recover by rewriting existing data.

While this process can recover the actual lost capacity, reported capacity continues to rely on the old data-to-parity ratio. An expanded vdev can continue to report a lower than expected capacity, even after rewriting old data to the new parity ratio. This accounting inconsistency does not impact the actual available capacity of the vdev.

For more information, see Jim Salter’s article at Ars Technica and the upstream RAIDZ extension PR, sponsored by iXsystems, at OpenZFS. See also “ZFS RAIDZ Expansion Is Awesome but Has a Small Caveat” by Louwrentius for an in-depth discussion of lost capacity and recovering overhead.

To extend a RAIDZ VDEV, go to Storage. Locate the pool and click Manage Devices on the Topology widget to open the Poolname Devices screen.

Select the target VDEV and click Extend to open the Extend Vdev window.

Select an available disk from the New Disk dropdown menu. Click Extend.

A job progress window opens. TrueNAS returns to the Poolname Devices screen when complete.

ZFS supports adding VDEVs to an existing ZFS pool to increase the capacity or performance of the pool. To extend a pool by mirroring, you must add a data VDEV of the same type as existing VDEVs.

You cannot change the original encryption or data VDEV configuration.

To add a VDEV to a pool: Click Manage Devices on the Topology widget to open the Poolname Devices screen. Click Add VDEV on the Poolname Devices screen to open the Add Vdevs to Pool screen.

Adding a vdev to an existing pool follows the same process as documented in Create Pool. Click on the type of vdev you want to add, for example, to add a spare, click on Spare to show the vdev spare options.

To use the automated option, select the disk size from the Automated Disk Selection > Disk Size dropdown list, then select the number of vdevs to add from the Width dropdown. To add the vdev manually, click Manual Disk Selection to open the Manual Selection screen.

Click Add to show the vdev options available for the vdev type. The example image shows adding a stripe vdev for the spare. Vdev options are limited by the number of available disks in your system and the configuration of any existing vdevs of that type in the pool. Drag the disk icon to the stripe vdev, then click Save Selection.

The Manual Selection screen closes and returns to the Add Vdev to Pool wizard screen (in this case the Spare option.)

You have the option to accept the change or click Edit Manual Disk Selection to change the disk added to the strip vdev for the spare, or click Reset Step to clear the strip vdev from the spare completely. Click either Next or a numbered item to add another type of vdev to this pool.

Repeat the same process above for each type of vdev to add.

Click Save and Go to Review to go to the Review screen when ready to save your changes.

To make changes, click either Back or the vdev option (i.e., Log, Cache, etc.) to return to the settings for that vdev. To clear all changes, click Start Over. Select Confirm then click Start Over to clear all changes.

To save changes click Update Pool.

To expand a pool by replacing disks, replace each with a higher capacity disk following the same procedure as in Replacing Disks. Insert the new disk into an empty enclosure slot and remove the old disk only after the replace operation is completed. If an empty slot is not available, you can offline the existing disk and replace it in place, but redundancy is reduced during the process.

1. Go to the Storage Dashboard and click Manage Devices on the Topology widget for the pool to open the Poolname Devices screen. Click anywhere on the VDEV to expand it and select one of the existing disks.

2. (Optional) If replacing disks in place, take one existing disk offline.

   

   Click Offline on the ZFS Info widget to take the disk offline. The button toggles to Online.

   Remove the disk from the system.

3. Insert a larger capacity disk into an open enclosure slot.

   

   a. Click Replace on the Disk Info widget on the Poolname Devices screen for the disk you off-lined.

   b. Select the new drive from the Member Disk dropdown list on the Replacing disk diskname dialog.

   

4. Add the new disk to the existing VDEV. Click Replace Disk to add the new disk to the VDEV and bring it online.

   Disk replacement fails when the selected disk has partitions or data present. To destroy any data on the replacement disk and allow the replacement to continue, select the Force option.

   

   When the disk wipe completes, TrueNAS starts replacing the failed disk. TrueNAS resilvers the pool during the replacement process. For pools with large amounts of data, this can take a long time. When the resilver process completes, the pool status returns to Online status on the Poolname Devices screen.

Wait for the resilver to complete before replacing the next disk. Repeat steps 1-4 for all attached disks.

TrueNAS automatically expands the usable capacity of the pool to fit all available space once the last attached disk is replaced.

You can always remove the L2ARC (cache) and SLOG (log) VDEVs from an existing pool, regardless of topology or VDEV type. Removing these devices does not impact data integrity, but can significantly impact performance for reads and writes.

In addition, you can remove a data VDEV from an existing pool under specific circumstances. This process preserves data integrity but has multiple requirements:

• The pool must be upgraded to a ZFS version that includes the device_removal feature flag. The system shows the Upgrade button after upgrading TrueNAS when new ZFS feature flags are available.
• All top-level VDEVs in the pool must be only mirrors or stripes.
• Special VDEVs cannot be removed when RAIDZ data VDEVs are present.
• All top-level VDEVs in the pool must use the same basic allocation unit size (ashift).
• The remaining data VDEVs must contain sufficient free space to hold all of the data from the removed VDEV.

When a RAIDZ data VDEV is present, it is generally not possible to remove a device.

To remove a VDEV from a pool:

1. Click Manage Devices on the Topology widget to open the Poolname Devices screen.
2. Click the device or drive to remove, then click the Remove button in the ZFS Info pane. If the Remove button is not visible, check that all conditions for VDEV removal listed above are correct.
3. Confirm the removal operation and click the Remove button.

The VDEV removal process status shows in the Task Manager (or alternately with the zpool status command). Avoid physically removing or attempting to wipe the disks until the removal operation completes.