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Re: Enabling UFS soft updates / journalling

On Sun, 23 Jun 2013, Steven Chamberlain wrote:

The release notes for 9.0-RELEASE [3] seems to imply that UFS+SUJ became
the default but I can't find evidence of the change happening in code.

Note that when combined with UFS snapshots, UFS+SUJ has some problems, and on stable/9 after 9.0-release, snapshots were disabled when SUJ was enabled. I'm not finding a good citation for this, though. (Maybe http://lists.freebsd.org/pipermail/freebsd-fs/2012-March/013996.html) Newer snapshots of stable/9 (and I think 9.1-RELEASE as well) should be more sane/safer.

[3]: http://www.freebsd.org/releases/9.0R/relnotes-detailed.html#FS

To implement UFS+S on Debian GNU/kFreeBSD would be a simple change in
d-i to use "newfs -U", but we may want it to be a user-configurable
option too.  It cannot be changed while a filesystem is mounted so only
the installer can do it, or using tunefs from a rescue system.

Any thoughts?

My biggest question is why upstream FreeBSD chose not to use this on the
root filesystem if it was safe enough for the others.  If it was, for
example, a bootloader limitation it may not be relevant to us.

I think it was general conservatism, and is no longer the case anyway.

Do these modes of UFS satisfy dpkg's expectations to be able to operate
safely?  (I think so, and furthermore dpkg makes very liberal use of
fsync() since ext4 was first introduced).

Is there a link to documentation of dpkg's expectations?

-Ben Kaduk

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