Date: Fri, 1 Feb 2002 23:39:49 +0100 (CET) From: BOUWSMA Beery <freebsd-user@dcf77-zeit.netscum.dyndns.dk> To: stable@freebsd.org Cc: Jesper Skriver <jesper@freebsd.org> Subject: Re: mount the same filesystem read-only on multiple boxes, and read-write on one ? Message-ID: <200202012239.g11MdnQ01561@beerswilling.netscum.dyndns.dk> References: <20020201195701.F21826@FreeBSD.org>
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Hejsa Jesper! %s wrote on %.3s, %lld Sep 1993 > The application would be a usenet news setup, where the overview and/or > spool would be mounted like this. Ewww. I'm not thinking too clearly, which is nothing new, but wouldn't one be also wanting to use synchronous (rw) mounts for something like this, in addition to not caching reads? I know nothing about how softupdates may play into the equation. I mean, it was a beauteous thing to stand in front of news-feed02 and wonder if it was still online, until many seconds later, a disk light would wink as it weaseled its way towards the top (shut UP about my cheating already). Somehow I can't imagine that every one of the 20-some news articles per second it received were being sent to the disk immediately. I'd also wonder about mmap()ed data, not that I know much about it. One may recall many many months back where one of my goals with FreeBSD was to use mmap() in a way to cause an absolute minimum of disk access to and from a random-access file. I'm going to assume that the overview and spool are large, append files, which makes life easier. Basically the thing I worry about is that both the overview and spool reflect accurately on disk, that which the kernel wants to toss to disk, immediately, lest the read-only slaves lose synchronization and present a messed-up view to readers. Buffering and caching sound like your enemies. Though probably nowhere near as severely as on some news swervers I've had the misfortune of reading from. (But Jesper, I thought you had given up news long ago, like me, to do Something Useful with your life ;-) barry bouwsma, ex-newsbastard To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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