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Newsgroups: comp.unix.bsd.freebsd.misc Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.rmit.EDU.AU!news.unimelb.EDU.AU!munnari.OZ.AU!spool.mu.edu!howland.reston.ans.net!newsfeed.internetmci.com!delmarva.com!udel!news.mathworks.com!uunet!in1.uu.net!quack!quack.kfu.com!nsayer From: nsayer@quack.kfu.com (Nick Sayer) Subject: Re: MFS - Why? Message-ID: <npX7tgO@quack.kfu.com> Sender: news@quack.kfu.com (0000-News(0000)) Organization: The Duck Pond public unix, +1 408 249 9630, log in as guest. References: <AEn4jRr0u3@qsar.chem.msu.su> Date: Wed, 29 May 1996 20:29:08 UTC Lines: 32 I don't claim to be too knowledgeable about it, but I do have one pragmatic reason for using MFS on /tmp/: A lot of the time swap space is unused. Why? Because you have to plan for a maximum case, not an average case. Disk space you set aside for swap is therefore essentially wasted unless you spend a lot of time near maximal VM allocation. This is the one thing other OSes that have VM (win95, macos) have over Unix: they use unused disk space as swap transparently while Unix must have explicitly allocated swap (this is not a Unix slam. Those who know me will know I am a Unix fan. These OSes make up for this one convenience with massive inconveniences of their own, and a case can be made that having control over swap can prevent all sorts of problems caused, for example, by runaway allocations). Since this is the case, what MFS does is it allows you to not spend any additional space on /tmp/. If you're going to run sort on a 6 MB input, it's going to want to put 6 MB of sort files in /tmp/. That's 6 MB of your root partition. Again, it is necessary to set aside space for the maximal use of /tmp/. More essentially wasted space unless you spend most of the time filling up /tmp/. So you can use one bit of excess capacity for a second purpose rather than creating two spaces larger than necessary. This is one of those cases where the cost:benefit ratio is very, very close to 1:1, but the benefit does exceed the cost, IMHO. -- Nick Sayer <nsayer@quack.kfu.com> | N6QQQ @ N0ARY.#NORCAL.CA.USA.NOAM | Is it a "hate crime" to +1 408 249 9630, log in as 'guest' | hate Big Brother? URL: http://www.kfu.com/~nsayer/ |