Date: Wed, 10 Jan 2007 11:38:01 -0200 From: "Victor Loureiro Lima" <victorloureirolima@gmail.com> To: freebsd-fs@freebsd.org, freebsd@scottevil.com Subject: Re: skipping fsck with soft-updates enabled Message-ID: <ac00e00a0701100538m16395e87t2fbf69acfeeb04ed@mail.gmail.com> In-Reply-To: <200701101139.l0ABdJ9K088810@lurza.secnetix.de> References: <45A3C96A.6030307@scottevil.com> <200701101139.l0ABdJ9K088810@lurza.secnetix.de>
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>From rc.conf man page:
---
background_fsck_delay
(int) The amount of time in seconds to sleep before starting
a background fsck(8). It defaults to sixty seconds to allow
large applications such as the X server to start before disk
I/O bandwidth is monopolized by fsck(8).
---
You can set the delay as long as you want, so it wont have to start
right away, in fact it can start as late as a year (if thats really
what you want ;))
att,
victor loureiro lima
2007/1/10, Oliver Fromme <olli@lurza.secnetix.de>:
> Scott Oertel wrote:
> > I am wondering what kind of problems would occur, besides lost space, if
> > after a system crash a fsck is skipped. According to the documentation,
> > with soft-updates enabled, the file system would be consistant, there
> > would just be lost resources to be recovered which I am assuming can be
> > safely done at a later time to avoid long periods of downtime during
> > peek hours.
>
> I think that's exactly what the background fsck feature
> does. If you enable it (which is even the default), the
> fsck process doesn' start right away, so the system comes
> up in multi-user mode immediately. Then a snapshot is
> created on the file system, and fsck runs on the snap-
> shot, freeing the lost space in the file system.
>
> Of course, it only works reliably with soft-updates enabled,
> _and_ there must not be any unexpected inconsistencies.
> However, with some common setups (e.g. cheap disks lying
> about completed write operation) it is difficult to
> guarantee the consistency. Soft-updates is rather fragile
> when the hardware doesn't work exactly as it's supposed to.
> I've witnessed breakage in the past, and for that reason
> I always disable the background fsck feature. And it's the
> reason I'm looking forward to gjournal to become stable,
> because it seems to be less fragile in the presence of
> imperfect hardware.
>
> Best regards
> Oliver
>
> --
> Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
> Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd
> Any opinions expressed in this message may be personal to the author
> and may not necessarily reflect the opinions of secnetix in any way.
>
> "C++ is to C as Lung Cancer is to Lung."
> -- Thomas Funke
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