TrueNAS 27 RC.1 ships with Linux 6.18 and OpenZFS 2.4

iXsystems released TrueNAS 27 RC.1 on October 5, 2026, the near-final build of the next major version of its storage operating system. It moves TrueNAS to the Linux 6.18 LTS kernel and OpenZFS 2.4, Phoronix reports. TrueNAS turns a server into a NAS, a network-attached storage box that shares files with every machine on a network. The stable 27.0 release is expected in early December, so home-lab owners and IT teams have about two months to test it.

Why it is called 27, not 26

This release was going to be TrueNAS 26. The developers renamed it because most users will end up running it in 2027 rather than 2026, Phoronix reports. The version number now matches the year most people will deploy it.

RC.1 means release candidate 1. It is the build the developers expect to ship as final unless testing turns up serious bugs.

What is new in TrueNAS 27

The base layers changed first. Linux 6.18 is a long-term support kernel, a version that receives fixes for years. OpenZFS is the filesystem that stores and protects the data. A filesystem decides how files are laid out on disks.

TrueNAS's own feature post lists the headline changes:

Feature	What it does	Editions
TrueSearch	Server-side file indexing, with macOS Spotlight Search integration	All
WebShare	Browser-based file access with Spotlight integration; requires TrueNAS Connect	All
Fusion Pools 2.0	RAIDZ special vdevs and a special vdev used as a SLOG	All
Live dataset tiering	Part of Fusion Pools 2.0	Enterprise only
Stateful SMB failover	Keeps Windows file-sharing sessions alive when a controller fails	Enterprise HA only
TrueNAS Object Interface	Early-access S3 access to ZFS datasets	All
LXC containers	Now fully supported	All

A few of those terms need a plain explanation. A vdev is a group of disks that ZFS treats as one unit. A SLOG is a fast device that speeds up writes that must be confirmed right away. S3 is the storage interface Amazon popularized, which many backup and app tools already speak. LXC containers are lightweight Linux environments that share the host's kernel.

Faster dedup and encryption

Two performance changes come from OpenZFS 2.4. TrueNAS says "dedup writes are up to 25% faster." Dedup, or deduplication, stores identical blocks of data only once to save disk space. It has a reputation for slowing writes, so any speedup there matters.

Encryption also gets quicker on newer processors. TrueNAS says "encryption is faster on CPUs with AVX2," a set of math instructions found in most modern x86 chips. The release adds user, group and project quotas, including default quotas for new datasets.

For high-availability systems, containers can now fail over between controllers, according to the TrueNAS documentation. High availability means two controllers run one system, so one can take over if the other fails.

How to upgrade

The documentation sets one rule. Users should "update to the latest maintenance release of the current major version before upgrading to the next major version." In other words, patch your current release fully first, then make the jump.

The notes also say no features are deprecated for future removal in TrueNAS 27, and none were removed in this version. That makes the upgrade lower-risk than a release that drops features.

What this means for developers

If you run TrueNAS in a lab or a small office, test RC.1 now rather than in December. Build a spare system or a virtual machine, restore a copy of your pool configuration, and confirm that your shares, apps and backup jobs still work. Report problems while the developers can still fix them before 27.0.

Teams that write to storage through scripts should look at the TrueNAS Object Interface. Early S3 access means tools that already talk to S3 could point at a ZFS dataset on your own hardware. Treat it as an experiment until it leaves early access.

If you turned dedup off because writes were too slow, measure it again on RC.1 with your real data. The 25% figure is TrueNAS's own, so check it against your workload before you count on it. Finally, note which features are Enterprise-only before you plan around them. Live dataset tiering and stateful SMB failover are not in the Community Edition.