Linux is deprecating EXT2 DAX mode by end of 2025 due to low adoption. Learn why DAX is being removed, migration options (EXT4/XFS/EROFS), and how this affects persistent memory users. Stay ahead with expert insights on kernel changes.
Introduction to EXT2 DAX and Its Upcoming Removal
The Linux kernel is set to deprecate Direct Access (DAX) mode for the EXT2 file-system, with complete removal planned by the end of 2025.
This decision, spearheaded by Jan Kara of SUSE, reflects the declining relevance of PMEM (Persistent Memory) technologies like Intel Optane DC, which were the primary drivers behind DAX adoption.
Key Takeaways:
EXT2 DAX mode allowed direct memory access to storage, bypassing the page cache for faster performance.
The feature was experimental and never gained widespread adoption.
Users relying on DAX are encouraged to migrate to EXT4, XFS, or EROFS, which still support it.
Why Is EXT2 DAX Being Deprecated?
The Rise and Fall of Persistent Memory
DAX was originally designed to work with non-volatile memory (NVM) solutions like Intel Optane DC Persistent Memory, which promised near-DRAM speeds for storage. However, Intel discontinued Optane in 2022, leaving DAX without a major use case.
Reasons for Deprecation:
Low Adoption – Few applications required DAX, making maintenance unjustified.
Better Alternatives – EXT4 offers full DAX support with better stability.
Simplified Kernel Code – Removing rarely used features reduces complexity.
"Since PMEM didn’t quite lift off, DAX isn’t as widely used as we originally hoped." – Jan Kara, SUSE
What Does This Mean for Linux Users?
Migration Paths for DAX Users
If you currently use EXT2 with DAX, you’ll see a warning message upon mounting:
"DAX enabled. Warning: DAX support in ext2 driver is deprecated and will be removed at the end of 2025. Please use ext4 driver instead."
Recommended Alternatives:
EXT4 – Fully supports DAX and is backward-compatible with EXT2.
XFS – A high-performance file-system with robust DAX implementation.
EROFS – Optimized for read-heavy workloads with DAX capabilities.
The Future of DAX in Linux
While EXT2’s DAX support is being phased out, the feature remains available in modern file-systems. This move highlights the Linux kernel’s focus on maintaining only widely used, efficient code paths.
Key Considerations for Developers & Sysadmins:
Evaluate storage needs – If DAX is critical, migrate to EXT4 or XFS.
Monitor kernel updates – The final removal will likely come in Linux 6.16 or later.
Check hardware compatibility – Ensure your NVM devices work with supported file-systems.
Frequently Asked Questions (FAQ)
Q: Will EXT2 itself be removed?
A: No, only DAX mode is being deprecated. The EXT2 driver remains intact.
Q: What happens if I keep using EXT2 DAX after 2025?
A: The feature will stop working in newer kernels, requiring a migration.
Q: Is DAX still useful without Optane?
A: Yes, but primarily in niche enterprise applications with other PMEM solutions.
Q: Which kernel version will drop DAX support?
A: Likely the last 2025 release, following the LTS kernel cycle.
Conclusion
The deprecation of EXT2 DAX marks the end of an experimental feature that never reached mainstream adoption. Users relying on direct access storage should transition to EXT4, XFS, or EROFS for continued support.
Next Steps:
Audit systems using EXT2 DAX.
Plan migration to a supported file-system.
Stay updated on kernel release notes for exact removal timelines.
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