TrueNAS SCALETrueNAS SCALE Nightly Development Documentation
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Create Pool

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

What's a pool? Storage pools attach drives organized into virtual devices called VDEVs. ZFS and TrueNAS periodically review and heal when discovering a bad block in a pool. Drives arranged inside VDEVs provide varying amounts of redundancy and performance. ZFS and VDEVs combined create high-performance pools that maximize data lifetime.

Review Storage Needs

We strongly recommend that you review your available system resources and plan your storage use case before creating a storage pool.

  • Allocating more drives to a pool increases redundancy when storing critical information.
  • Maximizing total available storage at the expense of redundancy or performance entails allocating large-volume disks and configuring a pool for minimal redundancy.
  • Maximizing pool performance entails installing and allocating high-speed SSD drives to a pool.
  • Security requirements can mean the pool must be created with ZFS encryption.
  • RAIDz pool layouts are well-suited for general use cases and especially smaller (<10) data VDEVS or storage scenarios that involve storing multitudes of small data blocks.
  • dRAID pool layouts are useful in specific situations where large disk count (>100) arrays need improved resilver times due to increased disk failure rates and the array is intended to store large data blocks. TrueNAS recommends defaulting to a RAIDz layout generally and whenever a dRAID vdev would have fewer than 10 data storage devices.

Determining your specific storage requirements is a critical step before creating a pool. The ZFS and dRAID primers provide a starting point to learn about the strengths and costs of different storage pool layouts. You can also use the ZFS Capacity Calculator and ZFS Capacity Graph to compare configuration options.

Creating a Pool

To create a pool using the Pool Creation Wizard.

Pool Creation Wizard Fields (Click to expand)

This wizard screen provides the option to configure a VDEV using the Automated Disk Selection fields. To individually find and select disks for a VDEV, click Manual Disk Selection in the Advanced Options area.

Choosing a dRAID VDEV layout removes the Manual Disk Selection button and adds different options to the Automated Disk Selection area. It also removes the Spare VDEV section from the pool creation wizard and replaces it with the Distributed Hot Spares option in the Data VDEV section.

VDEV Layouts

  • A Stripe designates that each disk is used sequentially in the VDEV. Requires at least one disk and has no redundancy. A data VDEV with a stripe layout irretrievably loses all stored data if a single disk in the VDEV fails. Not recommended for data VDEVs storing critical data.

  • A Mirror denotes that each disk in the VDEV stores an exact data copy. Requires at least 2 disks in the VDEV. Storage capacity is the size of a single disk in the VDEV.

  • RAIDZ and dRAID layouts each have 1, 2, and 3 options. These indicate the number of disks reserved for data parity and also the number of disks that can fail in the VDEV without data loss to the pool. For example, a RAIDZ2 layout reserves two additional disks for parity and two disks can fail without data loss.

Automated Disk Selection - Stripe, Mirror, and RAIDZ layouts

SettingDescription
Disk SizeSelect the disk size from the list that displays. The list shows disks by size in GiB and type (SSD or HDD).
Treat Disk Size as MinimumSelect to use disks of the size selected in Disk Size or larger. If not selected, only disks of the size selected in Disk Size are used.
WidthSelect the number of disks from the options provided on the dropdown list.
Number of VDEVsSelect the number of VDEVs from the options provided on the dropdown list.

Automated Disk Selection - dRAID layouts

Similar to RAIDZ, dRAID layout numbers (1, 2, or 3) indicate the parity level and how many disks can fail without data loss to the pool.

TrueNAS defaults to allocating 10 disks minimum as dRAID VDEV in Children. If creating a data VDEV with fewer than 10 disks, using a RAIDZ layout is strongly recommended for better performance and capacity optimization.

SettingDescription
Disk SizeSelect the disk size from the list that displays. The list shows disks by size in GiB and type (SSD or HDD).
Treat Disk Size as MinimumSelect to use disks of the size selected in Disk Size or larger. If not selected, only disks of the size selected in Disk Size are used.
Data DevicesData stripe width for the VDEV. Select the number of disks from the options provided on the dropdown list. TrueNAS recommends dRAID layouts have data devices allocated in multiples of 2.
Distributed Hot SparesNumber of disk areas to actively provide spare capacity to the entire VDEV. These areas are active within the pool and function in of adding a Spare VDEV to the pool. It is recommended to set this to at least 1. The Distributed Hot Spares number cannot be modified after the pool is created.
ChildrenThe total number of disks to allocate in the dRAID VDEV. The field selection and options update dynamically based on the chosen dRAID Layout, Disk Size, Data Devices, and Distributed Hot Spares. Increasing the number of Children in the dRAID VDEV can reduce the options for Number of VDEVs.
Number of VDEVsSelect the number of VDEVs from the options provided on the dropdown list. Options are populated dynamically depending on the selections made in all the other fields.
  1. Enter a name. Use up to 50 lower case alpha-numeric and permitted special characters that conform to ZFS naming conventions. The pool name contributes to the maximum character length for datasets, so it is limited to 50 characters.

    The pool name cannot change after creation.
  2. Create the required data VDEV.

    Select the layout from the Layout dropdown list, then either use the Automated Disk Selection fields to select and add the disks, or click Manual Disk Selection to add specific disks to the chosen Layout.

    dRAID layouts do not have the Manual Disk Selection button and instead show additional Automated Disk Selection fields. When configuring a dRAID data VDEV, first choose a Disk Size then select a Data Devices number. The remaining fields update based on the Data Devices and dRAID layout selections.

    Click Save And Go To Review if you do not want to add other VDEV types to the pool, or click Next to move to the next wizard screen.

  3. Add any other optional VDEVs as determined by your specific storage redundancy and performance requirements.

  4. Click Create Pool on the Review wizard screen to add the pool.