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Datasets Screens

  11 minute read.

Last Modified 2022-07-29 16:33 EDT

The Datasets screens, accessed from datasets on the Storage screen, display the configuration settings for datasets. Click the   and select Add Dataset to display the Add Dataset screen or click Edit Options to display the Edit Dataset screen.

Both the add and edit dataset screens display Basic Options settings to set up a simple dataset. Click Advanced Options to display more settings to further customize datasets.

Dataset Basic Options


Name and Options Settings

Parent pathRead-only field that displays the dataset path for the dataset. The root dataset path includes the only the name of the root dataset. Child datasets created from a child of root include the root dataset/parent dataset in the path.
NameEnter a unique identifier for the dataset. You cannot change the dataset name after clicking Save.
CommentsEnter notes about the dataset.
SyncSelect the sync setting option from the dropdown list. Standard uses the sync settings requested by the client software. Always waits for data writes to complete, and Disabled never waits for writes to complete.
Compression levelSelect the compression algorithm to use from the dropdown list. Options encode information in less space than the original data occupies. It is recommended to choose a compression algorithm that balances disk performance with the amount of saved space.
LZ4 is generally recommended as it maximizes performance and dynamically identifies the best files to compress.
ZSTD is the Zstandard compression algorithm with several options for balancing speed and compression.
Gzip options range from 1 for least compression with best performance, through 9 for maximum compression with greatest performance impact.
ZLE is a fast algorithm that only eliminates runs of zeroes.
LZJB is a legacy algorithm that is not recommended for use.
Enable AtimeSelect the access time for files option from the dropdown list. Access time can result in significant performance gains. Inherit uses the access time setting of the parent or the root dataset. On updates the access time for files when they are read. Off disables creating log traffic when reading files to maximize performance.

Encryption Options Settings

The default is Inherit selected. Clearing the checkbox displays more options. Selections in the Encryption Type field also displays additional setting options. See Storage Encryption for more information on encryption.

InheritSelect to use the encryption setting of the parent or root dataset (selected by default).
Encryption TypeSelect the option for the type of encryption to secure the dataset from the dropdown list.
Select Key to use key-based encryption. Displays the Generate Key option. Creating a new key file invalidates any previously downloaded key file for this dataset. Delete any previous key file backups and back up the new key file.
Select Passphrase to enter a user-defined passphrase to secure the dataset. This displays two additional Passphrase fields to enter and confirm the passphrase and the pbkdf2iters field.
Generate keySelected by default to have the system randomly generate an encryption key for securing this dataset. Clearing the checkbox displays the Key field and requires you to enter an encryption key you define.
Warning! The encryption key is the only means to decrypt the information stored in this dataset. Store encryption keys in a secure location!
KeyEnter or paste a string to use as the encryption key for this dataset.
AlgorithmDisplays for both key and passphrase encryption types. Select the mathematical instruction set that determines how plaintext converts into ciphertext from the dropdown list of options. See Advanced Encryption Standard (AES) for more details.
pbkdf2itersEnter the number of password-based key deviation function 2 (PBKDF2) iterations to use for reducing vulnerability to brute-force attacks. Entering a number larger than 100000 is required. See PBKDF2 for more details.

Other Options Settings

The Other Options settings help tune the dataset for specific data sharing protocols.


ZFS DeduplicationSelect the option from the dropdown list to transparently reuse a single copy of duplicated data to save space. Options are Inherit to use the parent or root dataset settings. On to use deduplication. Off to not use deduplication, or Verify to do a byte-to-byte comparison when two blocks have the same signature to verify the block contents are identical.
Deduplication can improve storage capacity, but is RAM intensive. Compressing data is recommended before using deduplication.
Deduplicating data is a one-way process. Deduplicated data cannot be undeduplicated!
Case SensitivitySelect the option from the dropdown list. Sensitive assumes file names are case sensitive. Insensitive assumes file names are not case sensitive. Mixed understands both types of file names. You cannot change case sensitivity after the saving the dataset.
Share TypeSelect the option from the dropdown list to define the type of data sharing the dataset uses to optimize the dataset for that sharing protocol. Select SMB if using with an SMB share. Select Generic for all other share types. You cannot change this setting after the saving dataset.

Data Compression Algorithms

Select the compression algorithm that best suits your needs from the Compression dropdown list of options.

LZ4 maximizes performance and dynamically identifies the best files to compress. LZ4 provides lightning-fast compression/decompression speeds and comes coupled with a high-speed decoder. This makes it one of the best Linux compression tools for enterprise customers.

ZSTD offers highly configurable compression speeds, with a very fast decoder.

Gzip is a standard UNIX compression tool widely used for Linux. It is compatible with every GNU software which makes it a good tool for remote engineers and seasoned Linux users. It offers the maximum compression with the greatest performance impact. The higher the compression level implemented the greater the impact on CPU usage levels. Use with caution especially at higher levels.

ZLE or Zero Length Encoding, leaves normal data alone but only compresses continuous runs of zeros.

LZJB compresses crash dumps and data in ZFS. LZJB is optimized for performance while providing decent compression. LZ4 compresses roughly 50% faster than LZJB when operating on compressible data, and is greater than three times faster for uncompressible data. LZJB was the original algorithm used by ZFS but it is now deprecated.

Advanced Options Settings

Advanced Options adds dataset quota management tools and more fields to the Other Options settings.

Dataset Quota Settings


Setting a quota defines the maximum allowed space for the dataset or the dataset and child datasets. You can also reserve a defined amount of pool space to prevent automatically generated data like system logs from consuming all of the dataset space. You can configure quotas for only the new dataset or include all child datasets.

Quota for this dataset
Quota for this dataset and all children
Enter a value to define the maximum allowed space for the dataset. 0 disables quotas.
Quota warning alert at, %Enter a percentage value to generate a warning level alert when consumed space reaches the defined level. By default, the dataset inherits this value from the parent dataset. Clear the Inherit checkbox to change the value.
Quota critical alert at, %Enter a percentage value to generate a critical level alert when consumed space reaches the defined level. By default, the dataset inherits this value from the parent dataset. Clear the Inherit checkbox to change the value.
Reserved space for this dataset
Reserved space for this dataset and all children
Enter a value to reserve additional space for datasets that contain logs which could eventually take up all the available free space. 0 is unlimited.

Advanced Other Option Settings

Many of the Other Options settings inherit their values from the parent dataset.


ChecksumSelect the checksum option from the dropdown list. Select Inherit to use the parent setting; On to use checksum without specifying the variant; FLETCHER2 (deprecated) or FLETCHER4 to use a position-dependent checksum that uses two checksums to determine single-bit errors in messages transmitted over network channels or ZFS streams; SHA256 (default for dedupted datasets) or SHA512 to use a sequence of numbers and letters to check the copy of a downloaded update file is identical to the original; SKEIN which is not supported for a file system on boot pools; or EDNOR which is not supported for file systems on boot pools and Edon-R requires verification when used with dedup so it automatically uses verify.
Read-onlySelect the option to allow or prevent dataset modification from the dropdown list. On prevents modifying the dataset. Off allows users accessing the dataset to modify its contents.
ExecSelect the option for executing processes from within the dataset from the dropdown list. On allows executing processes from within this dataset. Off prevents executing processes from with the dataset. We recommend setting it to On.
Snapshot directorySelect the option to controls visibility of the .zfs directory on the dataset from the dropdown list. Select either Visible or Invisible.


CopiesSelect the number of duplicate of ZFS user data stored on this dataset from the dropdown list. Select between 1, 2, or 3 redundant data copies. This can improve data protection and retention, but is not a substitute for storage pools with disk redundancy.
Record SizeSelect the logical block size in the dataset from the dropdown list of options. Matching the fixed size of data, as in a database, can result in better performance.
ACL TypeSelect the access control list type from the dropdown list of options. Inherit preserves ACL type from the parent dataset.
Off to use neither NFSv4 or POSIX protocols.
NFSv4 is used to losslessly migrate Windows-style ACLs across Active Directory domains (or stand-alone servers) that use ACL models richer than POSIX. Since POSIX ACLs are a Linux-specific ZFS feature, administrators should use NFSv4 to maintain compatibility with TrueNAS Core, FreeBSD, or other non-Linux ZFS implementations.
POSIX use when an organization data backup target does not support native NFSv4 ACLs. Since the Linux platform used POSIX for a long time, many backup products that access the server outside the SMB protocol cannot understand or preserve native NFSv4 ACLs. All datasets within an SMB share path must have identical ACL types.
For a more in-depth explanation of ACLs and configurations in TrueNAS SCALE, see our ACL Primer.
ACL ModeSelect the option that determines how chmod behaves when adjusting file ACLs from the dropdown list. See the zfs(8) aclmode property.
Passthrough only updates ACL entries that are related to the file or directory mode.
Restricted does not allow chmod to make changes to files or directories with a non-trivial ACL. An ACL is trivial if it can be fully expressed as a file mode without losing any access rules. Set the ACL Mode to restricted to optimize a dataset for SMB sharing, but it can require further optimizations. For example, configuring an rsync task with this dataset could require adding --no-perms in the task Auxiliary Parameters field.
Metadata (Special) Small Block SizeEnter a threshold block size for including small file blocks into the special allocation class (fusion pools). Blocks smaller than or equal to this value are assigned to the special allocation class while greater blocks are assigned to the regular class. Valid values are zero or a power of two from 512B up to 1M. The default size 0 means no small file blocks are allocated in the special class. Before setting this property, you must add a special class vdev to the pool.

Edit Dataset Screens

Click Edit Options on the Dataset Actions list of options to access the Edit Dataset screens.

The fields and settings on the Edit Dataset screens are the same as the Add Dataset screens but you cannot edit the Name, Case Sensitivity or Share Type fields on the Basic and Advanced Options screens.

Dataset Actions List

The Dataset Actions dropdown list options for child datasets are the same but also include Delete Dataset.

Add Dataset

The Add Dataset option displays the Add Dataset configuration screen where you can create a child dataset to the root dataset or to another child dataset.

Add Zvol

Add Zvol displays the Add Zvol where you can create zvols for a root or child dataset.

Edit Options

Edit Options displays the Edit Dataset screen where you can edit the settings for the selected dataset.

View Permissions

View Permissions displays the Dataset Permissions widget to the right of the root dataset on the Storagescreen. The Dataset Permissions widget is read-only.


OwnerDisplays the name of the owner, which is root for both the root dataset and the child datasets of root.
GroupDisplays the name of the group, which is root for both the root dataset and the child datasets of root..
PathDisplays the path for the selected dataset.
Unix PermissionsDisplays three levels of permissions, **Read

User Quotas

User Quotas displays the Set User Qutoas screen.

Group Quotas

Group Quotas displays the Set Group Qutoas screen.

Create Snapshot

Create Snapshot displays the One time snapshot of datasetname dialog where you can create a manual snapshot of the selected dataset. The dialog datasetname changes based on the name of the selected dataset (or zvol).


Name displays the system-created name for the snapshot.

Select Recursive to include child datasets or zvols in the snapshot of the parent or root dataset.

Click Create Snapshot to create the manual snapshot.

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