Thin Provisioning

Thin provisioning is a storage management technique used to optimize storage utilization and efficiency. It allows administrators to allocate storage capacity dynamically, on an as-needed basis, rather than allocating it all upfront.

Traditional thick storage allocation involves dedicating a specific amount of physical storage space for each zvol upfront, regardless of whether that space is immediately used. This can lead to inefficient use of storage resources and increased costs.

Thin provisioning, on the other hand, enables administrators to allocate storage space virtually, without immediately assigning physical storage. When a new zvol is created, it is assigned a size limit, but it consumes physical storage only as data is actually written to the volume. This allows for more flexible and efficient use of storage resources.

When creating zvols in TrueNAS, select to create the zvol as sparse.

Once a zvol is created, you cannot change the Sparse option through the GUI; you must recreate the zvol.

Thin provisioning helps your organization utilize storage resources more efficiently. By using the dynamic, in-line compression available in TrueNAS, you can maximize your available storage capacity.

Organizations can reduce capital expenditures on storage hardware by leveraging data-reduction features such as thin provisioning.

While thin provisioning offers flexibility and efficiency, organizations risk over-allocating storage capacity if they do not manage it properly. It is essential for organizations to configure and monitor free space alerts in TrueNAS to avoid unexpected depletion of physical storage.

When using TrueNAS to present block storage to devices that support TRIM or UNMAP functionality to reclaim disk space, organizations should create the underlying zvols as sparse volumes. This allows TrueNAS to coordinate with the guest operating system to free the underlying physical space on the storage, ensuring optimal space utilization and efficiency. Most modern operating systems and hypervisors default to this behavior, but organizations should verify it.

Windows Run the command fsutil behavior query DisableDeleteNotify in the command prompt and observe the results. If either filesystem shows that DisableDeleteNotify is set to 1, the TRIM functionality is disabled, and should be re-enabled.

Linux Run lsblk -D and verify that the contents of the DISC-GRAN and DISC-MAX columns are non-zero, indicating the granularity and maximum discard segment.

VMware Verify in the VMware UI that automatic space reclamation is enabled for your datastore.

You can also use the esxcli tools to confirm this by using the NAA ID of your datastore.