geom_raid5 inclusion in HEAD?

Arne Wörner arne_woerner at yahoo.com
Wed Nov 7 04:17:15 PST 2007


--- Ivan Voras <ivoras at freebsd.org> wrote:
> Arne Wörner wrote:
> I don't remember entire discussions about geom_raid5 but I seem to
> recall there was concern about its aggressive caching, possibly in the
> write path, which could make recovery in case of e.g. power outage
> problematic. I'm possibly mis-remembering this so feel free to ignore if
> it's not relevant to your geom_raid5.
> 
graid5 puts write requests for about kern.geom.raid5.wdt seconds (but not less
than 1-2 seconds) into the write cache (if there is enough space left in
graid5's write cache)... I would guess that this behaviour is pretty
incompatible with soft-updates with power outage...

Then there still is the write cache of the hard discs (I dont know how long it
waits, but that time would come in addition to graid5's delay)...

Maybe gjournal could help, because graid5 honors the BIO_FLUSH, but that is
untested...

-Arne

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