Hammer2 offline deduplication

Justin Sherrill justin at shiningsilence.com
Thu Nov 7 06:31:51 PST 2019

Are you looking for how it works technically, or how to operate it?
The design document goes into the technical details of how it's set


The design notes mention that, like you say, online dedup is on by
default.  There's no utility to run it offline yet, though I don't
know how much of a difference that makes in practice; online dedup may
already do most of the work.   I'd be interested in statistics on

On Wed, Nov 6, 2019 at 2:25 PM Mikhail Novosyolov
<m.novosyolov at rosalinux.ru> wrote:
> Hi,
> I have not been able to find documentation about how deduplication works
> in Hammer2. I have only found that online deduplication is now on by
> default, but there seems to be no description how it works.
> Is it possible to make offline deduplication? I mean finding blocks with
> the same checksum and making one block point to another instead of
> spending space on disk twice? There are several utilities that do this
> on BTRFS in Linux, for example https://github.com/Zygo/bees

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