Virtualization Disk Import and Export
A key improvement in TrueNAS 25.10-RC1 is the ability to import and export disk images within the Virtualization system. This feature supports various VM disk image formats, including VMDK, VDI, and QCOW2. Users can upload a disk image to a folder on their TrueNAS system, and the Virtualization service will ingest and convert it into a raw ZVOL for improved VM performance, with no need for manual command-line conversions. Exporting disk images helps facilitate easier VM portability or cloning, with further enhancements to come.
NVMe over Fabric Service Fixes
The new NVMe over Fabrics (NVMe-oF) service has received several fixes addressing initial issues and edge cases identified with delivering remote NVMe access during its wider testing period. These bug fixes aim to improve the stability and reliability of this new networking service; however, please note that both the NVMe/TCP and NVMe/RDMA services are not compatible with VMware initiators at this time.
Web UI and Middleware Bug Fixes
TrueNAS 25.10-RC1 includes several critical bug fixes to the middleware and Web UI:
- Feedback Button: The feedback button (the “smiley face icon in the taskbar) was not functioning in 25.10-BETA, requiring the manual submission of bug tickets and debug dumps. This has been corrected for RC1 (so keep those bug tickets coming!) restoring the way to get actionable bug reports and data to the TrueNAS engineering team.
- Empty SD Card Reader Blocking Pool Creation: A bug preventing proper pool creation when an empty SD card reader slot was present has been resolved. Users with embedded media readers should no longer receive an error message related to an unusable or “empty” block device.
- Empty SD Card Reader Breaks Temperature Reporting: The SD card reader issue was also determined to be causing problems with temperature reporting. The same logic that lets TrueNAS skip the unpopulated media reader slots also corrects this bug.
- Core to SCALE Upgrade Bug: An upgrade bug affecting systems that originated as early versions of FreeNAS or TrueNAS CORE and later migrated to SCALE has been fixed. This addresses issues for these legacy systems with specific partition layouts and corrects failures in the GRUB bootloader.
A Small Version Number brings Big Improvements – OpenZFS 2.3.4
This release upgrades the powerful OpenZFS filesystem of TrueNAS to version 2.3.4; and despite its small number bump over OpenZFS 2.3.3 in the BETA release, it introduces a wide range of improvements:
- MetaSlab Weight Calculation and Passivation Fixes: Improvements in the ZFS storage pool allocator allow for more accurate and more rapid decisions about where to place data on disks. This change reduces the variance of sync times when flushing transaction groups, particularly on fragmented pools.
- ZFS Block Clone Improvements: New block cloning defaults wait for pending dirty data flushes to prevent scenarios where a block-clone operation would fall back to a traditional copy instead. This may slightly slow small file operations but ensures data safety and preserves space efficiency.
- Memory Pruning and Reclaim Fixes: A combination of fixes for ZFS dnode pruning and memory reclaiming helps release more memory faster, preventing stalls and potential Out Of Memory (OOM) conditions when memory pressure is applied to ZFS ARC from outside workloads (like Virtualization)
- ARC Summary Enhancements: Adds an uncompressed size metric to the arc_summary script, providing better visibility into compression ratios and better representing the true size of the active data set being served by TrueNAS.
ZFS Rewrite Functionality
TrueNAS 25.10-RC1 continues the rollout of the zfs rewrite command, delivering a purpose-built, inline block file rebalancing method. This feature allows for under-the-hood rebalancing of data when drives are added or expanded, eliminating the need for manual file copying scripts. Because zfs rewrite operates entirely within ZFS, it ensures data integrity by avoiding the need to lock out files during the copy process, and even works with open files under active modification.
In addition to rebalancing pools after the addition of new drives, zfs rewrite can also relocate small files to optional special VDEV for acceleration. If you’ve used zfs rewrite to smooth out your pool – whether to rebalance after an expansion or for changing other settings – we’d like to hear how well it’s worked out for you, so send us some feedback using the (now-fixed) button in the taskbar.
(Optional) Web-Driven Installation
TrueNAS 25.10-RC1 fully supports the optional web-driven installation of TrueNAS Connect, detailed in our “Seamless Setup” blog. Designed to simplify the installation process, web-driven setup helps you get your TrueNAS system running and configured with a streamlined process that includes SSL certificate configuration and optional cloud-based alerting.
All This, and More
Whether you’re looking to upgrade from an earlier release or jump into TrueNAS for the very first time, there’s much more to learn about and love in TrueNAS 25.10. Check out our earlier blog on some of the Goldeye highlights and hardware support.
For conservative users, we currently recommend TrueNAS 25.04 for its maturity, Docker integration, and robust validation. For early adopters, TrueNAS 25.10-RC1 is ready for your eager review and feedback, with a clear upgrade path to the full release version of TrueNAS 25.10.0 at the end of October.
Ready to experience TrueNAS? You can download TrueNAS Community Edition to try it out, or if your business is ready to join the more than 60% of the Fortune 500 already using TrueNAS, reach out to our sales team and find out how the unified storage of TrueNAS can help you and your business take control of your storage.