EXT4 Deprecates Its Journaled "data=journal" Mode

7 days ago by cm0002 to c/linux

The EXT4 file-system today deprecated its journaled mode of the "data=journal" mount option. Following its deprecation, this mode is planned for removal in the year 2028.

The data=journal mode for EXT4 is where all file data and metadata is written to the file-system's journal before being committed to the main file-system. In the event of a crash or power loss, the journal can then be replayed to recover the data.

The EXT4 data=journal mode is great for those very concerned about data integrity and safety but comes with significant hits to the write performance compared to the default ordered (data=ordered) mode or data=writeback. Using the journaled mode also disables delayed allocation and Direct I/O support.

EXT4 journal deprecated

Per today's Git merge for Linux 7.3, the EXT4 data=journal feature is deprecated and support for it will be removed in early 2028 following the 2027 Linux LTS kernel version.

undefined 22 points 7 days ago

The plan is to stop journaling altogether? Isn’t that kind of a huge change, or am I missing something?

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frongt 6 points 6 days ago

No. The ext4 default mode is ordered, not journaled. The metadata is still journaled though.

I don't see any discussion on the kernel mailing list, though I've never gone looking for anything in there before.

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DaGeek247 5 points 6 days ago

Sounds like a big one to me. But I think it's also fair to say ext4 isn't really good for journaled data storage, especially compared to the competitors.

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refalo 5 points 6 days ago

Isn’t that kind of a huge change

Sortof... but almost nobody is actually using data=journal, as the default is ordered.

I do think it's important to keep it as an option though, so I disagree with removing it entirely. I suppose it could be forked into a separate module by someone who wants to maintain the journal support. I wonder if ext3's journaling will still be supported?

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ramius345 2 points 6 days ago

Reading through the phoronix comments, its default mode journals file metadata only instead of all writes.

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r3tr0_97 4 points 6 days ago

Can someone ELI5 it for me on what does this mean on a technical standpoint?

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