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List:       zfs-discuss
Subject:    Re: [zfs-discuss] [developer] Setting default user/group quotas[usage accounting]?
From:       Matthew Ahrens <mahrens () delphix ! com>
Date:       2012-04-30 15:56:28
Message-ID: CAJjvXiGg7ihXTLBbD_r0XNjax6CWq07eg8JZ9i97uDKQyWnd-w () mail ! gmail ! com
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2012/4/25 Richard Elling <richard.elling@gmail.com>:
> On Apr 25, 2012, at 8:14 AM, Eric Schrock wrote:
>
> ZFS will always track per-user usage information even in the absence of
> quotas. See the the zfs 'userused@' properties and 'zfs userspace' command.
>
>
> tip: zfs get -H -o value -p userused@username filesystem
>
> Yes, and this is the logical size, not physical size. Some ZFS features
> increase logical size
> (copies) while others decrease physical size (compression, dedup)

The size accounted for by the userused@ and groupused@ properties is
the "referenced" space, which is used as the basis for many other
space accounting values in ZFS (e.g. "du" / "ls -s" / stat(2), and the
zfs accounting properties "referenced", "refquota", "refreservation",
"refcompressratio", "written").  It includes changes local to the
dataset (compression, the "copies" property, file-specific metadata
such as indirect blocks), but ignores pool-wide or cross-dataset
changes (space shared between a clone and its origin, mirroring,
raid-z, dedup[*]).

--matt

[*] Although dedup can be turned on and off per-dataset, the data is
deduplicated against all dedup-enabled data in the pool.  Ie,
identical data in different datasets will be stored only once, if
dedup is enabled for both datasets.
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