Date: Sat, 22 Apr 2023 14:20:29 -0400 From: Paul Mather <paul@gromit.dlib.vt.edu> To: Andrea Venturoli <ml@netfence.it> Cc: questions@freebsd.org Subject: Re: ZFS on root with dedupe Message-ID: <21DC1470-EFCF-481D-BD3E-0C1C2BD9B5E1@gromit.dlib.vt.edu> In-Reply-To: <dc8b4e38-eaae-a4f7-c04d-a787d6f0b3ea@netfence.it> References: <edfdb11f-c423-09ce-9d89-2a7859dcfbb5@webtent.org> <361F0E2D-C885-4491-9D66-CC077CEE1BB4@gromit.dlib.vt.edu> <dc8b4e38-eaae-a4f7-c04d-a787d6f0b3ea@netfence.it>
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On Apr 22, 2023, at 1:52 PM, Andrea Venturoli <ml@netfence.it> wrote: > On 4/22/23 17:46, Paul Mather wrote: >=20 >> Deduplication is a per-fileset option >=20 > Oh! > I always thought it was a per-pool setting!!! > Did it change, perhaps after the switch to OpenZFS? I believe it has always been a per-fileset property. I think it is seen = as a "per-pool" setting because of the performance impact it can have on = the entire pool by enabling it on a fileset. ( > In fact the handbook says: >=20 >> To activate deduplication, set the dedup property on the target pool: >> # zfs set dedup=3Don pool >=20 > Isn't this incoherent? > I mean: > zfs set ... *dataset* > *zpool* set ... pool >=20 > Should it be corrected? The handbook appears out of date in this case. Even the example, as you = point out, is confusing because it references a zfs(8) command, which = acts upon filesets. For 13-STABLE (and the most recent 13.2-RELEASE), the zfsconcepts(7) and = zfsprops(7) manual pages both refer to deduplication being enabled for a = "file system" or "dataset". The zfsprops(7) manual page includes the = "dedup" property in per-fileset (or dataset as the manual page calls it) = properties: "Configures deduplication for a dataset." The = zfsconcepts(7) manual page states, "If a file system has the dedup = property enabled, duplicate data blocks are removed synchronously." I = interpret "file system" to be the same as fileset/dataset. These are = fileset/dataset properties, not pool properties. It's difficult to keep the FreeBSD Handbook accurate because it = potentially covers many simultaneous supported versions of FreeBSD. I = always treat the manual pages for an installed FreeBSD version to be = more accurate than the Handbook. Cheers, Paul.
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