*BSD News Article 7097


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From: bad@flatlin.ka.sub.org (Christoph Badura)
Subject: Re: Adding Swapspace ??
Organization: Guru Systems/Funware Department
Date: Mon, 26 Oct 1992 23:46:39 GMT
Message-ID: <Bwr61s.7At@flatlin.ka.sub.org>
References: <Bw7H4L.LLB@cosy.sbg.ac.at> <1992Oct16.162729.3701@ninja.zso.dec.com> <1992Oct16.201806.21519@fcom.cc.utah.edu> <Bw8Mw5.IFC@pix.com> <1992Oct18.082017.22382@fcom.cc.utah.edu> <BwLLxp.7Bt@flatlin.ka.sub.org> <1992Oct25.111525.25782@fcom.cc.utah.edu>
Lines: 21

In <1992Oct25.111525.25782@fcom.cc.utah.edu> terry@cs.weber.edu (A Wizard of Earth C) writes:
>I tend to use these terms synonymously.  When can a cache be write through
>but not write behind?  To "write through" a cache requires that the data be
>placed in the cache on it's way to the disk.  On the other hand, a write behind
>requires that the data be placed in the cache prior to being put on the disk.
>Is the distinction drawn on the idea that there may be a few microseconds more
>delay wherein the data is in the cache but not yet on the disk?

A cache architecture is "write through" when written data is
immediatly and synchronously written to secondary storage. "Write
behind" cache puts the data only into the cache, and writes it out to
secondary storage, when the cache fills up (or the cache line is to be
reused, in direct mapped architectures). 

That is (as far as I know anyway) the common definition.

-- 
				Christoph Badura  ---  bad@flatlin.ka.sub.org

AIX is a better... is a better...  is a better... OpenSystem.
					IBM Rep at GUUG Symposium '92