A TrueNAS dataset is a file system within a data storage pool. Datasets can contain files, directories, and child datasets, and have individual permissions or flags.

Datasets can also be encrypted. In TrueNAS 22.12.3 or later, the TrueNAS UI requires encryption for child datasets created in encrypted parent datasets, but you can change the encryption type from key to passphrase. You can create an encrypted dataset if the parent is not encrypted and set the type as either key or passphrase.

Which is it, bit or byte? And what is the difference between a bit or a byte?

Both bit and byte are basic measurements for computerized data but they represent different measurements.

A bit is the smallest unit of measure for computerized storage, and when combined with a time measurement such as seconds, becomes the common basis for determining how fast raw data bits transfer across a network, as in bits per second (bps). It is the basic unit of measurement for network bandwidth. A bit is the raw data unit, and is either a zero (0) or one (1). A bit is represented in measurements as the lower case b as it kilobits (kbs), megabits (Mbs), gigabits (Gbs), etc. When discussing the rate of speed as in bits per second (b/s or bps) you see measurements as Kbps for kilobits/second, Mbps for megabits/second, Gbps for gigabits/second, etc.

A ZFS Volume (zvol) is a dataset that represents a block device or virtual disk drive. TrueNAS requires a zvol when configuring iSCSI Shares. Adding a virtual machine also creates a zvol to use for storage.

To create a zvol, go to Datasets. Select the root or non-root parent dataset where you want to add the zvol, and then click Add Zvol.

The Disks screen lists the physical drives (disks) installed in the system. The list includes the names, serial numbers, sizes, and pools for each system disk.

Use the Columns dropdown list to select options to customize disk the information displayed. Options are Select All, Serial (the disk serial number), Disk Size, Pool (where the disk is in use), Disk Type, Description, Model, Transfer Mode, Rotation Rate (RPM), HDD Standby, Adv. Power Management, Enable S.M.A.R.T., S.M.A.R.T. extra options, and Reset to Defaults. Each option displays the information you enter in the Edit Disk screen or when you install the disk.

The zvol screens and widgets, accessed from the Datasets screen, allow you to add or edit a zvol and manage the volume storage. Zvols are listed on the Datasets screen tree table.

The tree table includes storage space used and available for that zvol (or dataset), encryption status (locked, unlocked, or unencrypted), and the role of that zvol or dataset or what service uses it (i.e., the system dataset, a share, virtual machine, or application).

TrueNAS uses ZFS data storage pools to efficiently store and protect data.

The Pool Creation Wizard configuration screens include a configuration preview and an inventory list of disks available on the system.

Create Pool at the top right of the Storage Dashboard screen opens the Pool Creation Wizard.

Configuration Preview lists pool and VDEV settings that dynamically update as you configure settings in the wizard.

Inventory displays the number of available disks by size on the system, and this list dynamically updates as disks move to VDEVs added in the wizard.

The Storage Dashboard screen allows users to configure and manage storage resources such as pools (VDEVs) and disks. The dashboard widgets organize functions related to storage resources.

The No Pools screen displays before you add the first pool.

The Datasets screen and widgets show information about datasets, provide access to data management functions, indicate the dataset roles, list the services using the dataset, show the encryption status, and list the permissions the dataset has in place. The screen focuses on managing data storage including user and group quotas, snapshots, and other data protection measures.

The Datasets screen shows No Datasets with a Create Pool button in the center of the screen until you add a pool and the first root dataset.