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Date:      Thu, 22 Oct 2015 15:15:10 +0200
From:      Julien Cigar <jcigar@ulb.ac.be>
To:        "Brandon J. Wandersee" <brandon.wandersee@gmail.com>
Cc:        Adam Vande More <amvandemore@gmail.com>, FreeBSD Questions <freebsd-questions@freebsd.org>, krad <kraduk@gmail.com>
Subject:   Re: gjournal and TRIM: A safe combination?
Message-ID:  <20151022131510.GY87605@mordor.lan>
In-Reply-To: <86lhaw107r.fsf@WorkBox.Home>
References:  <867fmh12nq.fsf@WorkBox.Home> <CALfReyfg-71nCg4K0dKmUK-YmZ8yi0ppeGGv4WOD-2Mt8NP9HQ@mail.gmail.com> <86pp081glq.fsf@WorkBox.Home> <CA%2BtpaK0ezoi7wBBD9VZwREq9Qp0YaJNfJY42=tZAYi5VSL8rCA@mail.gmail.com> <20151021143525.GX87605@mordor.lan> <86lhaw107r.fsf@WorkBox.Home>

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On Wed, Oct 21, 2015 at 02:38:16PM -0500, Brandon J. Wandersee wrote:
>=20
> Julien Cigar writes:
> > Correct me if I'm wrong but, unless there is a bug in Soft Updates (SU),
> > your FS will, in theory, never be corrupted with SU only.
>=20
> If I read this right, then, would gjournal be overkill for typical
> desktop/laptop use?  UFS2 is perhaps the only filesystems I've ever
> encountered in common use that doesn't have data journaling enabled by
> default, so that's thrown me off somewhat...

It depends of your needs, but for a typicaly desktop use it seems a bit
overkill to me.

Contrary to other filesystems UFS doesn't need journaling to avoid=20
_corruption_ as SU is an alternate approach to maintain metadata
integrity.

One important thing to remember is that neither SU, or SU+J, or any
journaled metadata prevents data loss: corruption !=3D data loss. This is
where gjournal (and data=3Djournal on EXT-like FS) comes in as datas and
metadatas are written in the journal _before_, so you avoid corruption
and data loss.

I hope SU+J will be fixed one day ...

>=20
> --=20
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
>    		      :: Brandon Wandersee ::
>                   :: brandon.wandersee@gmail.com ::
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> 'A common mistake that people make when trying to design something
> completely foolproof is to underestimate the ingenuity of complete
> fools.'
>                             			- Douglas Adams
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> _______________________________________________
> freebsd-questions@freebsd.org mailing list
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rg"

--=20
Julien Cigar
Belgian Biodiversity Platform (http://www.biodiversity.be)
PGP fingerprint: EEF9 F697 4B68 D275 7B11  6A25 B2BB 3710 A204 23C0
No trees were killed in the creation of this message.
However, many electrons were terribly inconvenienced.

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