From owner-freebsd-hackers Thu Jun 18 15:47:14 1998 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id PAA00716 for freebsd-hackers-outgoing; Thu, 18 Jun 1998 15:47:14 -0700 (PDT) (envelope-from owner-freebsd-hackers@FreeBSD.ORG) Received: from freefall.pipeline.ch (freefall.pipeline.ch [195.134.128.40]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id PAA00703 for ; Thu, 18 Jun 1998 15:47:09 -0700 (PDT) (envelope-from andre@pipeline.ch) Received: from pipeline.ch ([195.134.140.4]) by freefall.pipeline.ch (Netscape Mail Server v2.02) with ESMTP id AAA359; Fri, 19 Jun 1998 00:45:45 +0200 Message-ID: <358998E2.32A7AF2F@pipeline.ch> Date: Fri, 19 Jun 1998 00:46:59 +0200 From: "IBS / Andre Oppermann" Organization: Internet Business Solutions Ltd. X-Mailer: Mozilla 4.03 [en] (Win95; I) MIME-Version: 1.0 To: spork CC: hackers@FreeBSD.ORG Subject: Re: Disk Cache References: Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG spork wrote: > > Hi, > > I have a question about FBSD's disk cache mechanism. What happens when > you run a SCSI-SCSI raid controller that contains it's own cache memory? You better spend the money on 'real' RAM, FreeBSD does a better job managing cache then every caching controller because FreeBSD 'knows' what it needs next, the caching simply reads ahead. > The kernel has no way of knowing that some things are already cached out > beyond the SCSI card, so I assume it would cache something that's already > cached, right? How do you work around that? Is there some way of telling There's only one 'workaround': disable caching in FreeBSD with the "sync" mount option. > it "hey, don't be very aggressive with your disk caching"? Or is it such > a low priority thing that memory isn't used for cache unless there's no > other use for it? Kinda, FreeBSD looks how much memory the applications need and takes the unused memory for disk caching, but it dosn't go under a certain level. -- Ändre To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message