Il 2017-10-02 21:35 Kai Krakow ha scritto:
Besides defragging removing the reflinks, duperemove will unshare your
snapshots when used in this way: If it sees duplicate blocks within the
subvolumes you give it, it will potentially unshare blocks from the
snapshots while rewriting extents.
BTW, you should be able to use duperemove with read-only snapshots if
used in read-only-open mode. But I'd rather suggest to use bees
instead: It works at whole-volume level, walking extents instead of
files. That way it is much faster, doesn't reprocess already
deduplicated extents, and it works with read-only snapshots.
Until my patch it didn't like mixed nodatasum/datasum workloads.
Currently this is fixed by just leaving nocow data alone as users
probably set nocow for exactly the reason to not fragment extents and
relocate blocks.
Bad Btrfs Feature Interactions: btrfs read-only snapshots (never tested,
probably wouldn't work well)
Unfortunately it seems that bees doesn't support read-only snapshots, so
it's a no way.
P.S.
I tried duperemove with -A, but besides taking much longer it didn't
improve the situation.
Are you sure that the culprit is duperemove? AFAIK it shouldn't unshare
extents...
Niccolò
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