On Sun, Sep 11, 2016 at 09:13:28PM +0200, Martin Steigerwald wrote:
> Am Sonntag, 11. September 2016, 16:44:23 CEST schrieb Duncan:
> > * Metadata, and thus mixed-bg, defaults to DUP mode on a single-device 
> > filesystem (except on ssd where I actually still use it myself, and 
> > recommend it except for ssds that do firmware dedupe).  In mixed-mode 
> > this means two copies of data as well, which halves the usable space.
> > 
> > IOW, when using mixed-mode, which is recommended under a gig, and dup 
> > replication which is then the single-device default, effective usable 
> > space is **HALVED**, so 256 MiB btrfs size becomes 128 MiB usable. (!!)
> 
> I donīt get this part. That is just *metadata* being duplicated, not the 
> actual *data* inside the files. Or am I missing something here?

   In mixed mode, there's no distinction: Data and metadata both use
the same chunks. If those chunks are DUP, then both data and metadata
are duplicated, and you get half the space available.

   Hugo.

-- 
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