Heinrich Rebehn rebehn at ant.uni-bremen.de
Sun Feb 22 07:06:29 PST 2004

Gabriel Ambuehl wrote:
> Hi Heinrich Rebehn,
> you wrote.
>>>Make sure you've disabled write caching on the drive firmware
> HR> Does this also apply for RAID disks (twe)? Also, there is no word about
> HR> this in man tuning(7). Is this more of a guess or is softupdates 
> HR> definately dangerous with wite cache enabled?
> I'd say it's the other way round: write cache is dangerous with
> softupdates. Softupdates itself is certainly better than no
> softupdates, even if it takes a slight performance drop by disabling
> write cache.
> I think you should disable the write cache on the 3ware cache (not
> sure whether there actually is one, mine don't come with any RAM
> sockets) anyway as you'll lose all data in there in the event of a
> crash.

Why that? I can imagine that i lose data in case of a power failure, but
why in case of a crash? And why is write cache only dangerous with
softupdates, as you wrote above?

I had always write cache enabled on my twe controller, but my problems 
with softupdates definetely started with 5.2

Since i found no word about disabling write cache in the FreeBSD 
handbook or in man tuning(7), i would really like to know, if this is 
just a rumour, or where does it come from?
> Regards,
> Gabriel

Heinrich Rebehn

University of Bremen
Physics / Electrical and Electronics Engineering
- Department of Telecommunications -

Phone : +49/421/218-4664
Fax   :            -3341

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