Pools

The Pools page is used to both create zpools and to cluster them to create a service. The main page shows the pools discovered on a local node:

In the above example pools pool1 and pool2 are both clustered and running on node-a, pool3 is an exported, unclustered pool and poollocal is only visible to node-a and therefore cannot be clustered.

Creating a Pool

To create a pool, navigate to ZFS -> Pools and then click the + CREATE POOL button on the main pools page to bring up the pool configuration page:

Fill out the Pool name field and select the desired structure of the pool from the Pool Mode list. The cluster supports three types of layout when creating vdevs for a pool:

dRAID (distributed raid) and RAIDZ are two different vdev layouts in ZFS, each offering distinct approaches to data redundancy and fault tolerance. RAIDZ is a traditional RAID-like structure that distributes data and parity information across multiple disks, while dRAID distributes hot spare space throughout the vdev, enabling faster rebuild times after drive failures.

Configure options according to your requirements - for a more in-depth discussion on options please see the HAC ZFS Tuning Guide:

Log Device

The log device (also referred to as SLOG or Seperate LOG) is a dedicated storage device in a ZFS pool that enchances the performance of synchronous writes; it is best practice to deploy an SSD or NVMe device. The log serves as a temporary storage area for data that is being written synchronously, ensuring that the data is safely logged before it is written to the main storage pool.

The log device is a stripe of either single or mirrored vdevs, defined when creating the first log vdev.

For example, to create a log consisting of mirrored vdevs select two or more devices when first creating the pool:

After clicking SUBMIT the pool will be created with the following structure:

pool: pool1
 state: ONLINE
config:

    NAME        STATE     READ WRITE CKSUM
    pool1       ONLINE       0     0     0
      raidz1-0  ONLINE       0     0     0
        sdc     ONLINE       0     0     0
        sdd     ONLINE       0     0     0
        sde     ONLINE       0     0     0
    logs
      mirror-1  ONLINE       0     0     0
        sdf     ONLINE       0     0     0
        sdm     ONLINE       0     0     0

errors: No known data errors

Additional mirrored vdevs can be added if required.

Cache Device

ZFS keeps a data cache in the systems main memory, referred to as the ARC (Adaptive Replacement Cache - the algorithm used by ZFS to cache data). The pool itself can hold a second tier of cache on a dedicated cache device. The vdev itself can only be a stripe of individual devices, as mirrors etc. are not supported in cache vdevs.

Spare Device

A ZFS spare device is a disk that is designated to automatically replace a failed or faulted device in a ZFS storage pool, helping to maintain data availability and system reliability. It is not actively used in the pool until needed, allowing for seamless recovery from disk failures. Multiple spare devices can be added to a pool. They can also be shared between pools - simply select an existing spare when creating/editing a pool.

Special Device

A ZFS special device is a vdev dedicated to storing a pools metadata in preference to storing that data in the pools regular vdevs. Therefore adding a dedicated SSD/NVMe special device can have significant performance improvements, especially when the pool consists of many small files.

When special vdevs are added to a pool they become an integral part of that pool, i.e. should the special vdev become unavailable then the whole pool will be unavailable. For this reason it is critical to introduce redundancy when creating/adding a special vdev; at the very least it should be mirrored. For more information please see here.

Mirrored Pool

Mirrored pools are created by striping together individual mirrored vdevs.

Start by creating an individual mirrored DATA vdev (in this example a two way mirror is created, but these could be three, four way mirrors etc). Select drives for the vdev from the Available Disks list and click DATA to add them as data vdevs - in this example sdm and sdn are used to create the first mirror:

To configure multiple striped mirrors, select the next set of drives using the same number of drives as the existing data vdev, click DATA, then from the popup menu select + New vdev (note that selecting vdev-0 would extend the existing vdev rather than creating a new one):

This action will then add a further pair of mirrored drives to the pool layout, creating a mirrored stripe; additional drives are adding in the same manner:

Add further vdevs as required, here a log and a cache have been added:

Once configuration is complete, click SUBMIT and the pool will be created and displayed in the main pools page ready for clustering. The configuration of the pool can be checked by clicking the expand/collapse arrow on the left hand side of the pool entry:

JBOD/Stripe Pool

A jbod pool is a stripe of disks in a single vdev with no redundancy. Select individual disks and add them to the vdev using the DATA button:

Next click SUBMIT - the pool will be created and displayed in the main pools page.

RAIDZ2 Pool

For this example a RAIDZ2 pool consisting of two five drive vdevs striped together, a log, a cache and a spare will be created. Five disks are selected for the first vdev, the desired Pool Name entered and raidz2 chosen from the Pool Mode list:

Click on DATA from the Add selected disks menu to configure the first vdev:

Next the second vdev is added, again using five drives, but this time selecting + New vdev from the DATA menu:

The resulting configuration depicts the two vdevs striped together:

Next a log disk is added by selecting one of the remaining available drives and clicking the LOG button:

The same is done for a cache and spare device giving the final configuration:

Finally click SUBMIT - the pool will now be created and will show up in the main pools page.

Toggle the down arrow next to the pool name for details. Device information is shown by clicking Show on the devices line:

Editing a Pool

To edit a pool, navgate to ZFS -> Pools and then from the Actions menu for the pool to be edited select Edit Pool. This will present a summary of the pools current configuration:

Properties

To edit the properties of the pool click the EDIT button on the properties panel:

Make any required changes and click SAVE to update the pool properties (Pool Name, Pool Mode and Alignment Shift are immutable).

Pool Topology

To view the current topology of a specific vdev type click the arrow next to the vdev name:

To add or extend the pools vdevs click the + ADD button next to the specific vdev and select the drives from the list of available devices; in this example a additional raidz2 Data vdev is being added:

Finally click CREATE VDEV to add it to the pool:

When you have finished editing a pool, click DONE to return to the pools page.

Preparing a Pool to Cluster

Pools must be imported on one of the nodes before they can be clustered. Check their status by selecting the Pools option on the side menu.

In the following example pool1 and pool2 are already clustered and pool3 is going to be added to the cluster:

Firstly the pool need to be imported; select the Import Pool item from the Actions menu:

The status of the pool should now change to Imported and CLUSTERABLE:

The pool is now ready for clustering.

Clustering a Pool

Select the Cluster this pool item from the Actions menu:

Fill out the description and select the preferred node for the service:

With a shared-nothing pool the GUID's for each pool will be shown:

To add a virtual hostname to the service click Add in the Virtual Hostname panel. Enter the IP address, and optionally a hostname. For nodes with multiple network interfaces, use the drop down lists to select which interface the virtual hostname should be assigned to:

Finally, click the Create button; the pool will now show as CLUSTERED: