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From: terry@cs.weber.edu (A Wizard of Earth C)
Subject: Re: Adding Swapspace ??
Message-ID: <1992Oct25.111525.25782@fcom.cc.utah.edu>
Sender: news@fcom.cc.utah.edu
Organization: University of Utah Computer Center
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>
Date: Sun, 25 Oct 92 11:15:25 GMT
Lines: 33
In article <BwLLxp.7Bt@flatlin.ka.sub.org>, bad@flatlin.ka.sub.org (Christoph Badura) writes:
|> In <1992Oct18.082017.22382@fcom.cc.utah.edu> terry@cs.weber.edu (A Wizard of Earth C) writes:
|> >I think this was the pre 4.3 code, before the introduction of cluster groups;
|> >in any case, the write to the disk is done through a write-through cache.
|> The UNIX FS buffer cache has since it's invention been write-behind
|> and not write-through.
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?
Either situation requires the data to be in cache before it is on the disk.
Just curious as to why you draw such a sharp distinction, the point being that
there is negligible overhead in a cached writes for swap no matter how you
slice the pie.
Terry Lambert
terry@icarus.weber.edu
terry_lambert@novell.com
---
Any opinions in this posting are my own and not those of my present
or previous employers.
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