Re: Btrfs progs release 6.19

[joshua <joshua@mailmag.net>]

For what it’s worth, (not much) I used --convert-to-block-group-tree on a large fs with precious data (~10 drives, ~100Tb, Raid1 data, Raid1C3 metadata) and had no issues.

Convert took a LONG time, but afterwards, all my data integrity checks passed, scrub passed, and mount times are approximately 1 second now, compared to minutes previously.

—Joshua Villwock

> On Mar 24, 2026, at 6:00 PM, Christoph Anton Mitterer <calestyo@scientia.org> wrote:
> 
> On Tue, 2026-03-17 at 17:34 +0100, David Sterba wrote:
>>> How about migrating an existing fs to use the block-group-tree
>>> (with
>>> btrfstune --convert-to-block-group-tree)... has that also been well
>>> tested and is considered safe to be used on filesystems with
>>> precious
>>> data?
>> 
>> The in-place conversions are a bit more tricky as they start from an
>> existing filesystem and there's a possibility of finding some corner
>> case. Last time this was in 6.15.
> 
> I see. Thanks for the information.
> 
> 
>> It should be doable to test the conversion using device mapper
>> snapshot
>> devices on an existing valuable filesystem without destroying it.
> 
> But that would only tell me if the bug actually happens (and is
> noticed) during conversion... not if something is simply stored in a
> wrong way which I may not notice until much later (when it might
> already be too late).
> 
> Thanks anyway :-)
> Chris.
>