Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!ncar!mephisto!bbn.com!levin
From: levin@bbn.com (Joel B Levin)
Newsgroups: comp.sys.mac.programmer
Subject: Re: RAM Cache corrupt multi-user databases?
Message-ID: <55749@bbn.BBN.COM>
Date: 4 May 90 15:18:06 GMT
References: <1729.263cb9a5@vaxa.uwa.oz> <1990Apr30.212653.2004@uswmrg2.UUCP> <7986@goofy.Apple.COM>
Sender: news@bbn.com
Reply-To: levin@BBN.COM (Joel B Levin)
Organization: BBN Communications Corporation
Lines: 24

In article <7986@goofy.Apple.COM> chewy@apple.com (Paul Snively) writes:
|In article <1990Apr30.212653.2004@uswmrg2.UUCP> steve@uswmrg2.UUCP (Steve 
|Martin) writes:
|> In article <1729.263cb9a5@vaxa.uwa.oz> a_dent@vaxa.uwa.oz writes:
|> >I've read the technote about the RAM cache and I'm a little worried.  
|> >The RAM cache will only write its contents to disk when the application exits
|> >or the volume is flushed (or if a block is so old it gets bumped out).
|> I don't think this is correct.  As I recall the RAM cache that Apple has
|> implemented is a write-through cache.
|Bad news.  The original poster was correct; our cache isn't write-through. 
|And yeah, that does mean that your "writes" aren't really written until 
|the next FlushVol.

On the other hand, I believe that closing a file (the way that most
applications do) does a FlushVol; at least, closing a file will write
its cached (dirty) pages to disk at that time.  If you are opening and
closing files a lot this reduces your window of vulnerability a fair
amount.

	/JBL
=
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