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Path: euryale.cc.adfa.oz.au!newshost.anu.edu.au!harbinger.cc.monash.edu.au!news.mel.connect.com.au!munnari.OZ.AU!spool.mu.edu!howland.reston.ans.net!cs.utexas.edu!uwm.edu!news.cse.psu.edu!news.math.psu.edu!chi-news.cic.net!nntp.coast.net!fu-berlin.de!news.belwue.de!news.uni-stuttgart.de!news.ruhr-uni-bochum.de!news.rwth-aachen.de!newsserver.rrzn.uni-hannover.de!aix11.hrz.uni-oldenburg.de!uniol!uni-erlangen.de!news.tu-chemnitz.de!irz401!uriah.heep!news From: j@uriah.heep.sax.de (J Wunsch) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: MFS - Why? Date: 8 Jun 1996 15:19:49 GMT Organization: Private BSD site, Dresden Lines: 29 Message-ID: <4pc5ml$dsh@uriah.heep.sax.de> References: <AEn4jRr0u3@qsar.chem.msu.su> <4ogp99$kfu@nntp5.u.washington.edu> <ABgvNUrSgM@qsar.chem.msu.su> Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) NNTP-Posting-Host: localhost.heep.sax.de Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Newsreader: knews 0.9.6 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E "Eugene Radchenko" <eugene@qsar.chem.msu.su> wrote: > I guess I was not sufficiently clear in the original posting. If we have > merged disk cache/VM buffer and we open a file and write something to it, > then the data end up into that same buffer area as they would if we create > a file on the memory filesystem (with a difference that they could be > 'paged out' to normal filesystem if someone needs heaps of memory while the > MFS data could not). So what is the point? You still have a difference for metadata updates. For example, the creation and removal of a temp file cause two subsequent updates to the parent directory. I guess for FreeBSD-current and asynchronous metadata updates, the difference is almost not noticeable however. Of course, if your /tmp is in the root file system (and you wanna be safe and don't turn on async metadata updates for this one), you will notice the effect. Of course, MFS *is* swap-backed. It will be paged to the device you have been mounting it above, often the primary swap partition. Anyway, backing to a raw partition is probably still more efficient than backing to an underlying file system. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)