# OpenZFS zfs-2.4.0-rc5

- Product: OpenZFS (https://whatsnew.fyi/product/openzfs)
- Vendor: OpenZFS
- Date: 2025-12-11
- Version: zfs-2.4.0-rc5
- Original notes: https://github.com/openzfs/zfs/releases/tag/zfs-2.4.0-rc5
- Permalink: https://whatsnew.fyi/product/openzfs/releases/zfs-2.4.0-rc5
- Labels: Pre-release; Platforms: Linux

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **added** — Allow setting default user/group/project quotas
- **added** — Direct IO fallback to a light-weight uncached IO when unaligned
- **added** — Allow ZIL on special vdevs when available
- **added** — Extend special_small_blocks to land ZVOL writes on special vdevs
- **added** — Allow non-power of two values for special_small_blocks
- **added** — Add zfs rewrite -P which preserves logical birth time when possible to minimize incremental stream size
- **added** — Add -a|--all option which scrubs, trims, or initializes all imported pools
- **added** — Add zpool scrub -S -E to scrub specific time ranges
- **changed** — Release topology restrictions on special/dedup vdevs
- **changed** — Improve encryption performance using AVX2 for AES-GCM
- **changed** — Implement unified allocation throttling algorithm designed to reduce vdev fragmentation
- **fixed** — Multiple gang blocks improvements and fixes
- **fixed** — New dedup optimizations and fixes

We are excited to announce the fifth release candidate (rc5) of OpenZFS 2.4.0! 

###### Supported Platforms
- **Linux**: compatible with 4.18 - 6.18 kernels
- **FreeBSD**: compatible with releases starting from 13.3+, 14.0+

###### Key Features in OpenZFS 2.4.0:
- Quotas: Allow setting default user/group/project quotas (#17130)
- Uncached IO: Direct IO fallback to a light-weight uncached IO when unaligned  (#17218)
- Unified allocation throttling: A new algorithm designed to reduce vdev fragmentation  (#17020)
- Better encryption performance using AVX2 for AES-GCM  (#17058)
- Allow ZIL on special vdevs when available (#17505)
- Extend `special_small_blocks` to land ZVOL writes on special vdevs (#14876), and allow non-power of two values (#17497)
- Add `zfs rewrite -P` which preserves logical birth time when possible to minimize incremental stream size (#17565)
- Add `-a|--all` option which scrubs, trims, or initializes all imported pools (#17524)
- Add `zpool scrub -S -E` to scrub specific time ranges (#16853)
- Release topology restrictions on special/dedup vdevs (#17496)
- Multiple gang blocks improvements and fixes (#17111, #17004, #17587, #17484, #17123, #17073)
- New dedup optimizations and fixes (#17038, #17123, #17435, #17391)

###### How to Participate:

We encourage users and developers to test this release candidate and provide feedback. Your input is invaluable in ensuring the final release meets our community's needs. Please report any issues you encounter in our [GitHub repository](https://github.com/openzfs/zfs/issues/new/choose).

**zfs-2.4.0-rc5 changelog**: `git cherry -v remotes/origin/zfs-2.3-release zfs-2.4.0-rc5 |  sed '/^-/d; s/+ //g'`