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Date:      Sat, 05 May 2001 15:42:11 -0700
From:      "Kevin Oberman" <oberman@es.net>
To:        Nick Sayer <nsayer@quack.kfu.com>
Cc:        Doug Russell <drussell@saturn-tech.com>, stable <stable@FreeBSD.ORG>
Subject:   Re: soft update should be default 
Message-ID:  <200105052242.f45MgBc24741@ptavv.es.net>
In-Reply-To: Your message of "Sat, 05 May 2001 09:31:09 PDT." <3AF42ACD.5000500@quack.kfu.com> 

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> Date: Sat, 05 May 2001 09:31:09 -0700
> From: Nick Sayer <nsayer@quack.kfu.com>
> Sender: owner-freebsd-stable@FreeBSD.ORG
> 
> That may be the original intent, but cheap IDE drives let you turn on 
> write caching, and they're for sure not battery-backed (nor do they 
> attempt to store enough power at power-off to write back the cache with 
> the remaining rotational latency or any such trickery). They lie about it.
> 
> Write caching is evil unless you specifically know that it's being 
> battery backed. 99.44% of the time, that's not the case.

An obvious exception is the laptop. I always turn on write cache on my
laptop as I know that it has a LONG battery backup. For a worst-case
type of operation  (dd), I get 4x faster writes with write-cache
enabled on my laptop.

R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net			Phone: +1 510 486-8634

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