Date: Fri, 9 Oct 1998 11:21:54 +0200 From: Philippe Regnauld <regnauld@deepo.prosa.dk> To: Marius Bendiksen <Marius.Bendiksen@scancall.no> Cc: freebsd-current@FreeBSD.ORG Subject: Re: CDROM as system disk Message-ID: <19981009112154.45808@deepo.prosa.dk> In-Reply-To: <3.0.5.32.19981009083720.00929a20@mail.scancall.no>; from Marius Bendiksen on Fri, Oct 09, 1998 at 08:37:20AM %2B0200 References: <199810081905.MAA26707@usr08.primenet.com> <Pine.SGI.4.04.9810081555490.1189-100000@void.cs.rpi.edu> <3.0.5.32.19981009083720.00929a20@mail.scancall.no>
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Marius Bendiksen writes:
> >Slight problem, disk caching. If you are going to ping the drive every N
> >time units as a 'keep-alive', those blocks will very quickly get cached;
> >unless you devise some clever algorithm that will always ensure that you
> >get a block not in the cache (consider the cache could me a megabyte or
> >more in size, and this gets tricky)
>
> So, we'll need some function to flush the cache, or do uncached i/o...
We're talking about the CD-ROM's own cache. It's likely
you can't disable it on cheapo IDE models (some IDE guru
prove me wrong-- Søren ?), so you'll need to do like
mentioned before: read random blocks, _and stop doing that
while you're doing "legitimate" I/O_ (that means probably
hacking the driver in some way, with a timer).
--
-[ Philippe Regnauld / sysadmin / regnauld@deepo.prosa.dk / +55.4N +11.3E ]-
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