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From: df@phx.mcd.mot.com (Dale Farnsworth)
Newsgroups: comp.unix.wizards
Subject: Re: Should 'sync' stop terminal/system activity ? (SUMMARY)
Message-ID: <11616@mcdphx.phx.mcd.mot.com>
Date: 8 Sep 89 00:04:03 GMT
References: <265@atbull.UUCP> <266@atbull.UUCP>
Sender: listen@mcdphx.phx.mcd.mot.com
Reply-To: df@phx.mcd.mot.com (Dale Farnsworth)
Organization: Motorola Microcomputer Division, Tempe, Az.
Lines: 20

Andy Glew already gave a very good response on O(n^2) buffer flushing
algorithms and the problems this causes for large buffer caches.

I would like to elaborate on the Motorola's file system hardening switch.
Somebody wrote:

> Motorola's response was basically (1) set the file hardening switch
> (which turns the cache into a write-through cache -- at a tremendous
> performance hit), or (2) use fewer buffers.

Have you measured this "tremendous performance hit"?
Turning on file hardening does *not* make the cache write through.
It enables the standard SVR3 file hardening code which essentially
writes through critical directory and inode updates.
This file hardening greatly increases the integrity of the file system
in the event of a system crash.

I strongly recommend that no system run with file hardening disabled.

-Dale