Date: Sat, 19 Apr 2008 20:05:05 +0200 From: Mel <fbsd.questions@rachie.is-a-geek.net> To: freebsd-questions@freebsd.org Cc: Ivan Voras <ivoras@freebsd.org> Subject: Sidetracked: why gjournal over soft-updates (Was: Re: UFS2 Journaling implementation detail) Message-ID: <200804192005.06962.fbsd.questions@rachie.is-a-geek.net> In-Reply-To: <9bbcef730804180840y77adff73x7ad0cf90c82633a9@mail.gmail.com> References: <fu5nkb$3ib$1@ger.gmane.org> <790871.1688.qm@web57004.mail.re3.yahoo.com> <9bbcef730804180840y77adff73x7ad0cf90c82633a9@mail.gmail.com>
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On Friday 18 April 2008 17:40:04 Ivan Voras wrote: > > 5. "Some UFS implementations avoid journaling and > > instead implement soft updates: they order their > > writes in such a way that the on-disk file system is > > never inconsistent, or that the only inconsistency > > that can be created in the event of a crash is a > > storage leak. To recover from these leaks, the free > > space map is reconciled against a full walk of the > > file system at next mount." - > > (http://en.wikipedia.org/wiki/Journaling_file_system) > > > > So the disadvantage of Soft Update is it is necessary > > to run fsck after reboot in event of a crash or power > > failure? > > Yes. The advantage is that practically, the data is as safe as with > journalling. I've been following this with interest, however it's still not clear to me, why I'd want a journaling filesystem, because: 1) If you have soft-updates the data is as safe as with journal 2) If you have soft-updates fsck will run in the background 3) Soft-updates don't require diskspace. So...other then "journaling filesystems are cool", what's the real advantage? -- Mel Problem with today's modular software: they start with the modules and never get to the software part.
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