Gabriel Ambuehl wrote:
Hi Heinrich Rebehn,
you wrote.


Make sure you've disabled write caching on the drive firmware
itself...

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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