FreeNAS, TrueNAS monitoring

FreeNAS and TrueNAS monitoring in XorMon, open source under GPL v3, uses the REST API interface natively provided by the storage or, for TrueNAS SCALE depending on the version, the WebSocket API. XorMon graphs capacity, IO, data, latency and block size per pool, plus drive, port, cache, CPU and memory statistics, with health status and alerts.

Does XorMon support both FreeNAS and TrueNAS?

XorMon supports iXsystems FreeNAS and iXsystems TrueNAS, both listed among the supported storage systems, with one setup for FreeNAS / TrueNAS CORE and one for TrueNAS SCALE.

Each has its own tab below. OpenZFS, a separate entry in the same list, is monitored through the XorMon OS agent.

Sources: Storage monitoring, updated 2026-11-07, OpenZFS monitoring, updated 2026-11-06, and tabs below, updated 2026-11-10.

Which TrueNAS and FreeNAS metrics does XorMon monitor?

Per pool, XorMon graphs capacity, IO, data, latency and block size; per drive, IO, data, latency, busy and queue; per port, data, packets and errors.

The FreeNAS / TrueNAS tab of the feature matrix also lists CPU system, L1 and L2 cache hit and size, data access and prefetch data access, memory used and swap, health status, and performance and hardware event alerting. The feature matrix with all metrics adds compression ratio and snapshot capacity used per pool and per volume.

Sources: Feature matrix, FreeNAS / TrueNAS tab, and Feature matrix with all metrics, iXsystems and TrueNAS tabs.

Which TrueNAS API does XorMon use, REST or WebSocket?

XorMon uses the FreeNAS / TrueNAS CORE REST API interface; for TrueNAS SCALE, it can use the REST API or the WebSocket API, depending on the version.

TrueNAS SCALE provides two interfaces for collecting configuration and performance data: REST API and WebSocket API. API availability depends on the TrueNAS SCALE version, as the table in the TrueNAS SCALE tab below shows.

Sources: TrueNAS SCALE tab below, updated 2026-11-10.

How does XorMon connect to FreeNAS and TrueNAS?

XorMon connects from the XorMon host to the FreeNAS or TrueNAS storage on port 443, or port 80 in case of http, with an administrator account.

A read-only account is not enough: on TrueNAS SCALE, the built-in read-only role does not have access to all performance data XorMon collects, and on FreeNAS / TrueNAS CORE, only the system administrator account can connect to the REST API. The XorMon deployment table also lists port 443 for FreeNAS and TrueNAS.

Sources: installation steps below, updated 2026-11-10, and XorMon deployment.

Key points

  • Monitors iXsystems FreeNAS, TrueNAS CORE and TrueNAS SCALE through the API natively provided by the storage.
  • REST API for FreeNAS / TrueNAS CORE; REST API or WebSocket API for TrueNAS SCALE.
  • Pool: capacity, IO, data, latency and block size; drive: IO, data, latency, busy and queue.
  • Port data, packets and errors, plus CPU, cache, memory and swap statistics.
  • Health status, performance and hardware event alerts, open source license (GPL v3).

Installation and configuration for FreeNAS and TrueNAS

XorMon uses FreeNAS / TrueNAS CORE REST API interface natively provided by the storage to get all necessary data.
Supported are FreeNAS / TrueNAS CORE firmwares 11.2+ except version 24.10 (it has a bug in the API).

Storage connectivity

  • Enable access from the XorMon host to the FreeNAS storage on port 443 (80 in case http)

  • Storage user: root account must be used, unfortunately only root can connect FreeNAS REST API.

XorMon storage configuration

  • Add storage into configuration from the UI:
    Settings icon -> Device -> Storage -> New -> Vendor:device -> TrueNAS Core
    FreeNAS TrueNAS monitoring

  • Run "Test" for configured storage device, it must show "OK"

  • Wait about 1 hour, then reload the web browser, you should see it in XorMon UI

When configuring TrueNAS SCALE in XorMon, you need to select the API Type.

TrueNAS SCALE provides two interfaces for collecting configuration and performance data: REST API and WebSocket API.
Starting with TrueNAS SCALE 25.04, the new versioned JSON-RPC 2.0 WebSocket API is available and REST API is deprecated.
Versions 25.04 and 25.10 therefore represent a transition period where both REST and the new WebSocket API can be used.
Starting with TrueNAS 26, REST API has been removed and the WebSocket API must be used.

API availability depends on the TrueNAS SCALE version:

TrueNAS SCALE REST API JSON-RPC 2.0 WebSocket API
≤ 24.10 Supported No
25.04 Supported (deprecated) Supported
25.10 Supported (deprecated) Supported
≥ 26 No Supported

For simplicity, you can also select "Auto (detect by version)".


Storage connectivity

  • Enable access from the XorMon host to the FreeNAS storage on port 443 (80 in case http)

  • Storage user
    truenas_admin account must be used, unfortunately.
    The built-in ReadonlyAdmin role doesn't have access to all performance data we need to collect.

    Optionally, you can create an API key for the user and use it instead of a password.

XorMon storage configuration

  • Add storage into configuration from the UI:
    Settings icon -> Device -> Storage -> New -> Vendor:device -> TrueNAS SCALE

    TrueNAS SCALE monitoring

  • Run "Test" for configured storage device, it must show "OK"

  • Wait about 1 hour, then reload the web browser, you should see it in XorMon UI

Running arrays from several vendors? XorMon can monitor your storage systems in one place.

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