Date: Fri, 19 Jun 1998 00:46:59 +0200 From: "IBS / Andre Oppermann" <andre@pipeline.ch> To: spork <spork@super-g.com> Cc: hackers@FreeBSD.ORG Subject: Re: Disk Cache Message-ID: <358998E2.32A7AF2F@pipeline.ch> References: <Pine.BSF.3.96.980618173600.17695A-100000@super-g.inch.com>
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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
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