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DragonFly kernel List (threaded) for 2004-01
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Re: Background fsck

From: Chris Pressey <cpressey@xxxxxxxxxxxxxxx>
Date: Mon, 19 Jan 2004 11:25:51 -0800

On Mon, 19 Jan 2004 11:04:38 -0800 (PST)
Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> wrote:

> :On Mon, 19 Jan 2004 08:45:30 -0800 (PST)
> :Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> wrote:
> :
> :>     I really dislike the concept of a background fsck.  I don't
> trust:>     it.
> :
> :On Mon, 19 Jan 2004 09:28:30 -0800 (PST)
> :Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> wrote:
> :
> :>     I really dislike a R/W mount on anything dirty.
> :
> :Matt, I can appreciate that you feel a certain way, but, but, but,
> :you're not saying *why* and it's driving me bonkers.  :)
> :
> :-Chris
>     The problem is that while it is possible to make softupdates 
>     algorithmically robust in regards to recovery, softupdates itself
>     is such a complex beast that bugs have and will still be found
>     which create unexpected corruption on the disk during a failure.
>     [...]
>     So what does this all mean?  This means that if a power failure
>     occurs write smack in the middle of a disk I/O, all of
>     softupdate's careful block ordering could wind up for naught,
>     which means that unexpected corruption can creep in no matter what
>     you do.

Thank you :)

FWIW, I'm not actually very interested in this issue (I just wanted to
hear a balance of opinions, against bgfsck as well as for journalling.)

My own opinion is that the "speed-up-recovery-after-a-crash" thing,
while apparently a very sexy problem for filesystem programmers to
tackle, is going to become more and more of a non-problem as UPS's
become more and more consumer-friendly.

Like, if I can get one of these:


for $20US, and if it gives me enough time to sync everything to disc
before the power really goes out, then my HDDs will rarely power down in
an inconsistent state anyway, yes?


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