Path: utzoo!attcan!uunet!mcsun!ukc!edcastle!aiai!richard
From: richard@aiai.ed.ac.uk (Richard Tobin)
Newsgroups: comp.unix.internals
Subject: Re: RAM disk.
Message-ID: <3506@skye.ed.ac.uk>
Date: 10 Oct 90 14:35:20 GMT
References: <18560@rpp386.cactus.org> <143359@sun.Eng.Sun.COM> <18574@rpp386.cactus.org> <1850@necisa.ho.necisa.oz>
Reply-To: richard@aiai.UUCP (Richard Tobin)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 22

In article <1850@necisa.ho.necisa.oz> boyd@necisa.ho.necisa.oz (Boyd Roberts) writes:
>When I hear `ram disk' I reach for my revolver.  Now, repeat after me...

>    What is the buffer cache? -- A ram disk.

As has been pointed out elsewhere, there *is* a difference - most unix
filesystems will try to increase reliability by forcing certain writes
to take place synchronously.  This makes creating files faster on a ram
disk regardless of the buffer cache size.  Whether this affects you
depends on whether you write a few large files or lots of small ones.

However, it is reasonable for /tmp to be a filesystem which does not
do any synchronous writes, if you don't find it important to maintain
/tmp across crashes.  Once you do this, its performance should be
similar to (or better than) a ram disk.

-- Richard

-- 
Richard Tobin,                       JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,           ARPA:  R.Tobin%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.                UUCP:  ...!ukc!ed.ac.uk!R.Tobin